Steam/Garrys mod files help. U3

Alright, so I have a U3 version of Steam on my flash drive and I’ve got garrys mod on it and such, but I’ve ran into a problem. I don’t know how to find the steam folders or the garrys mod folders at all, so no addons. Need help accessing them or knowing if it’s imposable to edit u3 files installed on the flash drive.

[editline]11:00PM[/editline]

BUmp

Program Files>Steam>Steamapps>(your user name)>Garrysmod>garrysmod