How to Restore Steam Games [duplicate]

Help! I backed up my "common" folder when I reset my PC, but now, when I try to copy it into "steamapps", Steam doesn't detect the files AT ALL. I have really slow internet, so I'd be looking at about a week of re-downloading my 14 games if I can't resolve this!

I'm on windows 10.

You might not be able to restore just the common directory that contain the application binaries.

There are appmanifest files in the SteamApps directory itself, cache files scattered all over the place, and other pieces that provide context for the actual application binaries.

Steam can be run from a removable drive in so-called "portable mode". But you must backup the entire Steam directory.

For more information, see this question: How do I update my full list of games on my Offline PC?