Hi there and welocme to JA
Follow the upper radiator hose to the block. right there on the block will be your thermostat housing, take off this housing and you will see the thermostat make sure to remember which side the spring is facing.
On the ecotec engine, the thermostat is located in a different area than on most other engine designs.
If you look at the exhaust manifold, you will see underneath it a coolant pipe that connects to a small aluminum housing towards teh front of the engine. This housing is the location of the thermostat. To replace the thermostat you need to remove the exhaust manifold, the coolant pipe, and this small housing for access to the thermostat. (sorry about that, I didn't design it!)
Hope this is helpful!