Are you saying the ground pin came off the Motor Home's plug?
Replace the plug, Just get a new plug and replace it
There are 4 wires in the cord (cut it off with a hacksaw if you have to)
Green is the Safety Ground
White goes to the flat pin opposite the ground
Red and Black, or black and black to one or the other side flat pins, Does not matter which one is red and which one is black.
It's that easy, do not forget to clamp the cord and seal the cord to the plug body (Goop). Tighten all screws well, Inspect for stray wires (Also called short circuits) I like Power Pull, some do not. Make sure the plug you buy fits if you need to poke it into a small chamber.