Take out your mirror switch and look at the plug. Or, as a general rule of thumb (not 100% certainty) if your car as memory seats/mirrors you likely have the 12 pin plug. I'm assuming your car isn't facelifted, in which case you have the ribbon connectors. Search on e46fanatics.com for more info on this subject, and for pics of the two connectors in question.
'12 M3 6MT Alpine White + Fox Red Extended | '09 328i 6MT Space Gray + Black