Your drain for the fresh water tank is right below the fresh water tank at the rear of the camper and towards the driver side. As you know, you put city water in and fill the fresh water tank at the water-fill station at the left/rear and the water takes a short trip to the tank. The pump is below the kitchen cabinet to the far right nearest the slideout. Two screws hold the panel on and the water pump is easily visible or worked on
The drain is a white tube for the freshwater tank is a white tube that hangs down. Mine has a plastic threaded piece inserted and retained by a radiator clamp and a cap screw onto the thread from below. This may not be EXACTLY like your setup but the tube hanging down is easily visible (mine is about 8-9" long).