If you go into gamemode/gmstranded/gamemode/modules/world
You can replace the world files with the ones inside of the stargate_worlds folder. You will then need to have CAP installed and will need to manually create your gatespawner file as I did not include one.
Note.. this only works on the stargate map that we used on our server. If you want to use custom maps.. you'll need to look at the worlds files and figure out how they are configured then create your own for each of the worlds in your map.