On my 97, the knock sensors are threaded into the 1/8" pipe tapped holes that used to be where you drained the coolant from each side of the engine block. They screw vertically up into the angled underside ot the block, about an inch out from the edge of the oil pan. They are more or less centered between the flywheel and the timing cover. The rear sensor has a heat shield around it. You can see them both if you get under the car and look straight up on either side of the block.
If you need to remove them, be ready to catch the coolant that will drain each side of the block when you do.