The sensor is the wheel speed sensor, and on these cars it is part of the wheel bearing / hub assembly. The sensor may be fine; you won't know until you plug it in. The sensor should be plugged into a wiring harness that runs alongside the parking brake cable. I don't have any pics showing where it plugs in, but here you can see the parking brake cable running diagonally across the picture, and the wiring harness (with the ribbed plastic sheathing) clipped to it.
If that harness isn't there, you have a bigger problem. If it is there, plug in the sensor and see if you get the ABS light to clear. If it doesn't clear, then see if you can get the code pulled (to verify it is just that one sensor that is bad), and then you'll have to replace that rear hub / wheel bearing assembly.