Most trailer hitches are classed by tongue weight. Class ll is 250# class lll is 300# if you need to move the bunks and, or the axle to not have a over weighted tongue weight. Too heavy you have no steering control on the tow vehicle, and it wears out your front tires. Too light and the trailer sways at highway speeds. Use a bath room scale to weigh the tongue weight at towing height of the tow vehicle or parallel to the ground.
Karl