do anyone know were the themostat located on a 1997-nissan pickup.

not enough info.

Follow the top radiator hose. Where it connects to the engine is where the thermostat is.

Generally but not always. re:1973-79 Mercury Capri 2.6 & 2.8. The Tstat is in the lower hose at the front of the water pump.

But it is true on Nissan. At least every one I’ve owned and worked on.