Map for mods, where there from?

Hey all,

I have recently started playing Gmod again,
and i went to play some TTT and Zombie Survival, and found that i missing quite a few maps,

I have all the CS:GO maps, and every other Valve game i was aware of, but what games do i need to install to get the maps, like, i was missing cs_office, yet i have CS:S installed, so do i need to buy/install CS:GO?

cheers for the help guys!

CS:GO maps don’t work in GMod, and servers usually have FastDL where you can download the maps…

Start up and convert your CS:S and it should work.