480 this "dog bone " is for converting 30 amp 120 to 15 amp 120 travel trailer service it will not work for 240 volt 30 or 50 amp but i'am sure you already know thisGo to an RV/Camper stupply store and ask for a 'dogbone'.
It will look something like this:
They will only work if you have 4 wires in the 220v receptacle. Just make sure you know what type of 220 receptacle you have to plug into, so you can make sure you get the right kind of male cord end to match it.
Since you now have a 110v receptacle, you'll need to GFI-protect it with a GFI cord.