Thirty Amp cord for new Fifty Amp service

I now have a new Serenity with the 50 Amp service. I have several old connection cords for 30 Amp service and am wondering exactly how to convert one of these so it has the female end to connect to the 50 Amp receptacle on the trailer and will allow me to plug the 30 Amp male plug into my generator. Maybe someone can give me instructions on where to obtain a 50 Amp female plug and how to wire the 30 Amp cord. I suspect it is done by using only one side of the two hot wires of the 110v 50 Amp connection.



So, first i need the female plug, second the instructions how to wire it.



Thanks for any help.