You'd need to buy or borrow a SATA to usb adapter. They can be brought for about £/$10 and will allow you to hook up the old drive to the usb slot then act as a disk.
Would hooking both drives up as slave drives not act as the same thing? Both would still be accessible to transfer data from one, to another, correct? I don't understand why it has to be through a SATA to USB adapter.