The code you got from your radio is the serial number, you will need the card with the radio unlock code on it.
But if like me you were not provided that when you bought the car.....
There is a website I have used in the past, that with the radio serial number it will give you a list of three codes to try. One will work (I think you have 5 tries at it, so do not guess)
http://www.unlock-code.co.uk/radio_code_check.php?m=Becker
Also if you are in good with a dealership, they should be able to look it up for you also.
One other option, if you want the card from becker with the code on it.
http://www.beckerautosound.com/Code_request/Code%20Request%20Form.htm
Good luck