Hi and welcome
If you stereo is the face off Blaupunkt,
o don't really know if they have the same in earlier models tbh) then the code is as follows
Turn on stereo
Confirm the code entry by pressing 1
Enter first digit using the < (back) button
Confirm 1st digit pressing the 1 button
Enter 2nd digit with <
Confirm with the 1 button again
Follow the same steps until all the code is showing on the screen
If the correct code was entered the set will beep and function
If incorrect an error beeb will occur and then WAIT and display will show CODE
(the waiting period is increased each time an incorrect code is entered...1 minute 2 minutes etc)