The Republic of Korea (commonly known as South Korea) and the Democratic People's Republic of Korea (commonly known as North Korea) were simultaneously admitted to the United Nations (UN) in 1991. On 8 August 1991, the UN Security Council passed United Nations Security Council Resolution 702, recommending both states to the UN General Assembly for membership. On 17 September 1991, the General Assembly admitted both countries under Resolution 46/1.

Can we conclude that is south korea a member of the united nations?
yes