To be certain, you'll need to consult a repair manual specific to your 2001 Chevy Tracker's engine. A Haynes or Chilton manual would be a good resource, as they have diagrams and instructions. You can also find diagrams online through sites that specialize in automotive repair information, but be sure you find one that specifically mentions your engine size.
Simply searching for "2001 Chevy Tracker [1.6L or 2.0L engine] thermostat location" with your engine's displacement may also yield helpful images. Remember to always be cautious when working on your engine and consult a professional if you are unsure about any step.