Here are some more pieces of the hardware jigsaw, that you should have. However you might choose to buy something else, or find yourself with a different type of drive and interface.
Most good ones are very portable.
External SCSI drives may have problems with cables. What interface you have depends on what model you have. That interface circuitry is totally independent of the sound card, simply in the same package. Music from the CD into the sound channel went through an analogue wire and socket, like the microphone, only a different plug, and inside the case not outside. The manufacturers also produced a really cheap interface card, for people without sound cards.