A primary source is the raw, unanalyzed material that is the starting point and basis of all good research. A primary source can be anything that offers a first-hand account, such as letters, maps, photographs, paintings, a poem, the manuscript of a novel, a newspaper advertisement, a diary, census data, or statistics.
All good research is based on data, whether it is numbers, pictures, words or texts, or objects.
This data has to exist, and you must discover it and analyze it, for your research question to be proven. Sometimes the data is available, and sometimes it needs to be gathered. It will take more time than you think to gather your raw material, synthesize it, and draw conclusions about its relevance and meaning. Have a clear understanding of the focus of your topic and be able to explain it to the librarian helping you. Understand the language of the material because primary sources usually are not translated nor do they come with explanations written in English.