Best way to detect what’s above a part?

So I was think about how selling stuff would work in my game, Farming Simulator. I think I’m going to go for a system where you place a trailer with grain over a part and you go inside, talk to a NPC, and the grain gets unloaded. One thing is though, I’m not sure what the best way to getting what’s above the unloading part. I was thinking something like this.

*This is all from the top of my head. Some of it might be wrong.

This is the only way to do it that I can think of, but are there any better ways?