How to Wire a Dryer With 4 Wires to a 3 Wire Plug
The older 3P, 3-wire dryer circuits are still legal and safe to use, so there's no need to rewire your dryer branch circuit to install a new dryer that came equipped with a 4-wire "appliance whip" (wire). It's much easier and much less expensive to replace the 4-wire whip with a 3-wire whip.