How do Change the 4 wire pigtail on the dryer to a 3 wire to match the receptacle in a mobile home? What do I do with the green wire on my dryer?

There is usually a metal tab running from the center connector (neutral) on the terminal block to part of the metal casing. You can attach it there. Sometimes there is a hole outside of the terminal block cover that will have an arrow and say ground - attach it there. If either of these don't work for you attach it to the dryer body with a sheet metal screw.