You probably don't have the same manual that originally came with your car, or your radio has been changed at some time prior to your ownership.

You need to get the serial number of the radio, either by pressing buttons 1 and 6 together (which may or may not work) or pull the radio out from the dashboard slightly so that you can read the serial number that will be printed on a sticky label on the radio casing.

When you have the correct serial number please post again.