2006 stereo

I'd like to activate XM on my 2006 Tahoe, but, there is no XM module (that I can see) behind the glove box, and, there are no XM bands on the head unit. Now, my 2003 Tahoe ALSO does not have an XM tuner, BUT, it does have the XM bands on the head unit. I currently have an iPod adapter using the...