Need help locating the thermostat on a 1999 ford taurus station wagon.

Where the upper radiator hose attaches to the engine is the thermostat housing. Remove the hose from the housing. Remove the housing, the thermostat will come out with the housing. Be careful to orient the new thermostat exactly the same as the old. If the new thermostat is put in backwards the car will overheat.
Hope this is helpful.