Double and triple wide mobile homes have a single main panel from where electrical power is distributed. The electrical power to the section(s) without the main panel is concentrated in one or a few points at the marriage line where the parts of the home come together. When all the power to one section fails it almost certainly indicates some problem with the electrical crossover point(s).
At this point you will have to decide if you are ready, willing and able to crawl under the house and check things out. If you are, you will want to be sure you have everything you need the first time since it is not so much fun you will want to do it over and over.
You will want to study your owners manual (hopefully you still have it) to see exactly where the crossover point(s) are.
You will need:
-A good flashlight
-Knee pads if you have them
-Electrical test equipment
-A good idea where to look