You need 1/4" QIC drive - they were in the heyday 10-1t years ago before being eaten by DATs and other tape formats. Most of these are SCSI drives, so you will probably need appropriate controller as well. See e.g.
http://en.wikipedia.org/wiki/Quarter-inch_cartridge for trivia.
But - the most important thing is to know what software was used to write the data. Windows NT' Backup program used to support tapes, there (used to be) a lot of backup programs supporting tapes, Unix/Linux support tapes, and every program used it's own way to encode / compress the data.
If I was you, I would start with that - what program wrote these, and then move forward. Build a PC with a drive, controller, and load some Windows NT or Linux on it.