How do I get a radio code for my Nissan Micra K12 1.5 diesel 2003?

Hi, Im new to this forum. My battery died and my radio needs the code. I've searched through all the manuals in case it was written down. Im nervous about taking it to a dealer cos Im not the richest guy in the world. Can anyone help? Ive took the details from the back of the radio/cd player, they are:

Blaupunkt - Werkegmbh
BP 3349 3 6356756
Nissan MM CD-K
7643 349 318
e1 022458
(stamped in blue ink) F 373

Any help would be greatly appreciated. Thanks