Could be a livery pack for the official MiG-19P module or a community-made mod for the free version.
Use a tool like WinRAR or 7-Zip to open the .rar file. Locate Mod Folder: Download MiG19 Viet rar
Frequently distributed as "MiG-19 Vietnam" packs for Cold War campaigns. Typical Installation Steps Could be a livery pack for the official