Hello Truy, this should help.
First check in the glove box for a white sticker with 8 numbers on it, some dealers put the sticker with the serial number on it there.
NOTE: The original radio has a coded theft protection
circuit. Be sure to get the customer's code number
— disconnecting the battery.
— removing the No. 39 (7.5 A) fuse from the underhood
— removing the radio.
After service, reconnect power to the radio and turn it
on. When the word "CODE" is displayed, enter the customer's
5-digit code to restore radio operation.
1. Remove the rear console (see page 23-128).
2. Remove the front console panel.
Stereo Radio/Cassette Player
No. Wire Connects to
3. Remove the two screws. Pull the stereo radio/cassette
player out part of the way.
4. Disconnect the 16-P connector and antenna lead,
then remove the stereo radio/cassette player.