Right-click part01.rar and select "Extract Here" or "Extract to [Folder Name]" using software like WinRAR or 7-Zip.
: Microsoft officially delisted Forza Horizon 3 from the Microsoft Store in September 2020. Online features may be limited, and the game is no longer available for direct digital purchase. Forza.Horizon.3.part08.rar
: This usually means one of the parts, possibly part08.rar , is corrupted. You may need to redownload that specific part. Right-click part01