The key thing to remember when citing primary sources in your work is to provide enough information so that the reader can retrace your steps and find the same resource on their own.
Frequently, archives will provide information on their preferred citation style or format, usually labeled as "Citations," "How to Cite Materials From...," or similar phrasing, and provides information such as collection name; series, file, or item numbers; location; and dates.
Individual style guides, such as Chicago, Turabian, or MLA, will have sections or details on the information to include with primary source citations and any set formatting for listing order.