How do you remove a kitchen sink drain hole copper pipe?

Undo the whole embly under the sink or at least the broken part and take it to your local hardware store. You may not get copper but you will have a trap and all that other stuff you need. I think channel locks will be sufficient to loosen. PVC is the cheap way to go out and you will figure it out once you get started. Oh! Its screws on the bottom of the sink. Plumbers putty for 99 cents is a good gasket for reembly.