If mine is still there I’ll definitely be backing up that save.
EDIT: Whew, that was scary for a sec. I booted up JC3 and the game started as though new, ugh. But then of course I realized that I’d switched motherboard and processor and gone to Windows 10 on a new SSD in April of last year and found my Just Cause 3 folder in the backup I’d made then of the Documents folder. Once I plopped that in the place of the newly created one all was well.