They managed to get a quarter of the warehouse emptied out in the first trip.
But it took more than three trips for the rest. Mostly from them grabbing one last piece of equipment from the supply warehouse. Apparently the supplies included some concrete, steel bars, and building supports. They could expand their base on the outside to the surrounding buildings near City Hall!
All they needed was to create some solid concrete barriers and they were set. And thankfully they had a tool store nearby in the form of Dome Depot, Bowe's, and Hardhat supplies. They had plenty to work with and plenty of tools to farm for their needs.