I have a Briggs and Stratton 6250 storm responder generator that has a 4 prong 30amp plug on it, I purchased from Amazon an adaptor cord to convert it to operate my Montana High Country should I ever have the need until I obtain a quiet inverter generator. This is probably what you are looking for.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1