The Ministry for Foreign Affairs was established in 1791, when Gustav III established the Royal Cabinet for Foreign Correspondence. The body was formally named the Ministry for Foreign Affairs in 1840.
Utrikesdepartementet
There is an index of the archive in the National Archive Database (NAD): https://sok.riksarkivet.se/arkiv/JYMNeBUQrH6d0002H087k3 The National Archives has also published an extensive archival guide to the Ministry's archive, in Swedish: Romefors, Örjan, and Emre Olgun. _Utrikesförvaltningens källor 1520--2000_. Skrifter utgivna av Riksarkivet 39. Stockholm: Riksarkivet, 2017.