I think you need a radio that's compatable with the stacker.
Looking at my radio the 6 buttons under the cassette relates to the 6 cds in the stacker so when you select disc 1, pressing button 1 you can fiddle with the cd track you want to listern to, thus the requirement of the correct cable connection, do you want to connect to your original radio ??.
My radio is the same as that in the ZJ so a Alpine stacker is compatable.