Check the coupler near where the ball goes. the correct ball size should be stamped on V section that is welded to the frame. it will likely be a 2" but could be the larger one.
As for brakes, check under the frame by propane tanks. there should be an electric brake controller safety switch.... where you connect a wire from you tow vehicle so in the event the trailer comes unhitched, the electric brake on the trailer engages and stops the trailer.