odds are the hitch is a 5000-lb Class III. before you spend $ on a dolly you would be well advised to weigh the dolly, the toad and your MH as you load and configure it for travel. this would include fuel, water, LP, food, clothing, supplies, pets, people and other "stuff". get individual axle weights to ensure that neither axle weighs more than it's associated rating.
once you know the weight of your MH, your toad and your dolly you can determine if the combined weight of the toad/dolly combo is safe to tow. in general, the maximum amount of weight you can safely tow will be the lesser of the following:
• the GCWR (gross combination weight rating) of the MH minus the actual weight of the MH as it is loaded for travel (includes fuel, fresh water, food, clothing, people, pets, supplies, eyc)
• the weight rating of your tow bar
• the weight rating of your hitch
good luck to you.