OP - assuming we are talking about W10 or 11 and pc. If that is case, your sim files should be at the following place - you should copy them there. Then once complete delete the other stuff. If you miss something MSFS should fix it on the next load to play, as some self-analysis does take place. Backup your Community Folder first just to be safe. Let us know how it works out. Or you could delete all sim files, and reinstall again, your call.
C:\my profile\AppData\local\packages\Microsoftflightsimulator8blah blah.
Then the file errors should disappear. Now this belies enough space to move them there.
And others have put them on other drives, with varying success. I have 2TB primary C so I keep them there. Happy flying