3 prong 50 amp plug to 4 prong 50 amp ????

Like GlennLever (I'll bet) we are over 60 and remember when 120V only used two wires and 240V used three. Like him I have an adapter that lets me hook into my brothers 3 wire 240V welder outlet to power my MH. We can lead you to the water but we cannot make you drink. For those that cannot understand that the ground and neutral are one and the same at the circuit breaker box and cannot look outside and see that there are only three wires coming into your house; I guess you could run a neutral wire out of the 4 outlet box and plug it into your standard three prong 120V outlet so the neutral is still separated (until it gets to the circuit breaker) box if this will make things right.
I wonder how much liability insurance this guy has for selling this adapter?