If you have a ground wire, then just buy new outlets and wire them up. ie) there should be three wires - black, white, and bare. If you don't have a ground wire, you need a GFCI for the first outlet in the line. Check the existing 3-prong outlets to make sure they too have a ground wire. If not, put a GFCI on those circuits. The GFCI must be the first outlet from the breaker box. If you don't understand any part of this answer, then hire a pro. Or make sure your fire and life insurance are current.