Set System Serial Number Cd How Do You Remove The Radio On A 2000 Mitsubishi Galant?

How do you remove the radio on a 2000 Mitsubishi Galant? - set system serial number cd

The battery was dead in the car and made anti-theft radio in the factory. I do not have the card with the code on it when I bought the car. I need the serial number from the radio security code from a local dealer.