To be certain, you'll need to consult a repair manual specific to your 1997 Mercury Mystique 2.0L engine. A picture in the manual will definitively show its location. You can often find these manuals online (some are free, others are paid) or at auto parts stores.
Looking at diagrams or pictures online for a 1997 Mystique 2.0L engine's throttle body will also help you identify it visually once you've located the throttle body itself.