Most older vehicles use that setup. The Mustang has had a combination rotor/hub setup since the 60's. In 1994, Ford went to a separate rotor hub like all modern cars in which you just slide the rotor on and off the hub.
To change the rotors, you'll need to remove the dust cap and unscrew the nut and remove the rotor and bearings. You may need new bearings or bearing seals for the rotors as well.
If you are uncertain about a rotor change on a Fox body, pick up a Haynes or Chiltons and read it. It's important you do it correctly when the only thing holding your rotor on is a little nut that is torqued down in in-pounds.