What goblin camps are you talking about: the big ones that demand tribute or more like the smaller ones?
There’s this little tutorial that could help you with that, but it’s a while since it was written and may be outdated. Also note that it details how to create raiders rather than a camp, but the process is similar; you can look up the file goblin_raider_camp.json that’s located among the ambient threats campaign, that one creates a camp so you can use that to help create your own camp.