Originally Posted by bond7
What kind of cable do I use to copy music from my Macbook to the internal HDD?
That's not possible because both machines have only USB host ports. You cannot connect one host to another.
Get a nice big USB thumb drive, plug it into your Macbook, format it FAT32, copy your music onto it, dismount it cleanly (drag it to the trash can), plug it into the stereo and use the menus to load the music onto the hard drive.