Question: Where is Sherri Mitchell's tribe organized as a First Nations band government?

Context paragraphs:
Simpcw North Thompson Indian Band: The Simpcw First Nation, formerly known as the North Thompson Indian Band, is a First Nations band government based in the Thompson Country of British Columbia, Canada.  It is a member of the Shuswap Nation Tribal Council.  It is a First Nations government of the Secwepemc (Shuswap) Nation, located in the Central Interior region of the Canadian province of British Columbia.  The band's main community is at Chu Chua, British Columbia.  Four of the five First Nation Reserves in Simpcw territory were designated on July 5, 1877 and the fifth was designated on February 24, 1916.  The Shuswap language name for North Thompson Band's community and reserve is 'Simpcw'.

Skuppah Indian Band: The Skuppah Indian Band is a First Nations band government located near Spuzzum, British Columbia.  It is a member of the Fraser Canyon Indian Administration, one of three tribal councils of the Nlaka'pamux people.  Other members of the Fraser Canyon Indian Administration are the Spuzzum, Kanaka Bar and Nicomen First Nations (the Nicomen First Nation is also a member of the Nicola Tribal Association).

Esquimalt First Nation: The Esquimalt First Nation, also known as the Esquimalt Indian Band and Esquimalt Nation, is a First Nations band government of the Esquimalt people.  Historically their village was located closer to Victoria proper, but today their main reserve is on the north shore of Esquimalt Harbour adjacent to the Town of View Royal.  They are a member nation of the First Nations of South Island Tribal Council, and were signatories to the Douglas Treaties.

Waywayseecappo First Nation: The Waywayseecappo First Nation is a First Nations band government whose reserve is located twenty miles (32 km) east of Russell in Manitoba, Canada.  The First Nation's reserve is 10,059 hectare (24,856 acres) and is located near the southwestern corner of the Riding Mountain National Park.  It is bordered by the Rural Municipality of Rossburn and the Rural Municipality of Silver Creek.  The First Nation also hold interest together with 32 other First Nations on the 37.1 hectare (91.7 acre) Treaty Four Reserve Grounds (Indian Reserve No. 77), located adjacent to Fort Qu'Appelle.  Its population is 1,219 in 2011.  They are home of the MJHL team Waywayseecappo Wolverines.  There are various business located in the Birdtail valley near highway 45, such as gas station, RCMP station, food mart, gaming centre, health centre, daycare and community arena complex.  And as of April 1, 2014 the RMCP no longer be in the community and replaced by Dakota Ojibway Police Services.

Penobscot: The Penobscot ("Panawahpskek") are an indigenous people in North America with members who reside in the United States and Canada.  They are organized as a federally recognized tribe in Maine and as a First Nations band government in the Atlantic provinces.

Sherri Mitchell: Sherri Mitchell is a Penobscot attorney and activist from Maine.  Mitchell is an attorney with the Native American Unit of Pine Tree Legal Assistance.  She is also the executive director of the Land Peace Foundation, which is dedicated to the protection of indigenous land rights.  Mitchell has been actively involved with the Idle No More movement for indigenous rights in Canada and abroad.

Sandy Lake First Nation: Sandy Lake First Nation (or Negaw-zaaga'igani Nitam-Anishinaabe, Oji-Cree: ᓀᑲ ᕊᑲᐃᑲᓂᐣ) is an independent Oji-Cree First Nations band government.  The First Nations community, in the west part of Northern Ontario, is located in the Kenora District, 227 km northeast of Red Lake, Ontario.  Its registered population in June 2007 was 2,474.  As of December 2015 the total registered population reached 3,034.  Sandy Lake First Nation maintains an affiliation with Nishnawbe Aski Nation, as a signatory to the Treaty 5.

Huu-ay-aht First Nations: The Huu-ay-aht First Nations (HFN) is a First Nations band government based on Pachena Bay about 300 km northwest of Victoria, British Columbia on the west coast of Vancouver Island in British Columbia, Canada.  The HFN is a member of the Nuu-chah-nulth Tribal Council and is a member of the Maa-nulth Treaty Society.  It has recently completed and ratified its community constitution and has successfully ratified the Maa-nulth Treaty on 28 July 2007.  The Legislative Assembly of British Columbia passed the Maa-nulth First Nations Final Agreement Act on Wednesday, 21 November 2007 and celebrated with the member-nations of the Maa-nulth Treaty Society that evening.

Musqueam Indian Band: The Musqueam Indian Band (Halkomelem: "xʷməθkʷəy̓əm" ] ) is a First Nations band government in the Canadian province of British Columbia and is the only First Nations band whose reserve community lies within the boundaries of the City of Vancouver.

Cold Lake First Nations: The Cold Lake First Nations is a First Nations band government.  This band is the governing body for people descended from several different historic groups, hence the plural, "nations", used in the band's name.  In August 2016, there were 2,858 members of this band, of which 1,382 lived within five reserves, about 220 km2 large within the province of Alberta.

Supporting paragraphs: Sherri Mitchell Penobscot
Answer: the Atlantic provinces