So, I've seen this topic has already been covered and there's a solution, but I don't understand the fix. Where do I find the steam install file? Where is this file I'm supposed to move those saves into?

Your steam install directory is probably something like "c:/program files(x86)/steam". Inside that folder should be one called "userdata" and inside of that should be a bunch of folders with just numbers for names. You'll be looking for a recently modified one that contains your save files (which will end with .fos). You'll need to copy them back to your "documents/my games/fallout4/saves" directory.