Hey there. I had the Chevy version of this truck once upon a time. The location depends on what engine you have:
If you have a 4-cylinder, cap should be near the center on top of the engine. If it’s the 4.3L V6 the cap will be off to one side, but still on top. I think we’re looking at the v6 here.
Look for a black or yellow cap, it should say OIL.
Is there any way you can take a picture of the engine from directly above it?
It should be more towards the passenger side, maybe more forward then center. It may not say oil, but rather 5w-30 or something like that.