Visit excise department at Civic center with your original book/file, CNIC.
Go to the counter with respect to your number series, ask them that you want the new design plates to replace your yellow plates. Hand him over the documents that he requests, then he'll do some verifications, tax should be upto date. Pay 1800 at the same counter and then he will hand you over 2 printed forms, get one form stamped from where they are handing new number plates (on the right side as soon as you enter on first floor) and your process is done. All you have to do is wait for about a month.
When you go to collect your new number plates, you need to surrender your old yellow number plates.
