Stereo help CD changer 1993 100 CS

[SuffolkD at aol.com]

I got this Q:

I have a 1993 audi 100 cs quattro and recently purchased the stock 10 disk cd 
player.  I noticed you were talking about this on the audiworld forums.  
Would you be able to help me figure out how to attach it to the car?
I have found the cable from the car which is a 12 pin square connector and a 
round 13 pin cable on the cd player.  Am I missing the interface?  is it 
possible to splice them together?
-Scott by BOSTON