My astra radio is in safe mode, how do I enter the unlock code? ?

Hi, the Blaupunkt Car 300 radio/cassette in my astra has entered safe mode. Please send me the unlock code and instuctions how to enter the code.

Could you also tell me if I need to enter any other code, after the safe mode is cleared.

Model: GM0300X5224600

Serial No: 7 649 852 320

Thank you very much. This service and your kind help is greatly appreciated.

Chris