Source SDK missing games

I have recently decided to download source SDK to try out some modding on some source games. The three I currently own are tf2, cs:go and garry's mod.

However when I go onto the source SDK list I find no games are listed there. I tried to add the GMOD directory (/GarrysMod/garrysmod) which made the hammer editor work for it. But when I tried to use the model editor I was met with the error message "unable to load manifest file scripts/game_sounds_manifest.txt".

I then changed my directory to where this was kept and I received a different error.

I am guessing some file movements are needed due to the whole steampipe thing that has happened I believe. 

Has anyone else attempted these movements and/or fixed these errors.