To be certain, you should:
* Consult your owner's manual: This is the best source for the specific location on your model year.
* Look for a small, cylindrical canister: It's usually black plastic and may have some tubing connected to it.
* Search online for diagrams: Searching "Ford Windstar [year] charcoal canister location" on Google Images may provide helpful pictures.
Because it's under the car, you'll likely need to get down on the ground or use a jack and jack stands to safely view it. Remember to always prioritize safety when working under a vehicle.