I am trying to turn a kitchen in to a bedroom I need to find out how to properly cap off kitchen sink pipes please someone tell me how to cap them off

Depending on the material the pipes are you use permanent caps. For galvanized pipes you use threaded caps. For copper pipes you solder on hard caps and for PVC you glue on permanent caps. For a professional looking job I would open up the walls and cut the pipes back inside them. I would then cap the pipes and patch and paint the walls. Good luck, Tom