Before you do anything, you need to ask DELL what processors are supported by THEIR BIOS. An upgrade processor must be socket, BIOS, and chipset compatible.
I spoke to their representative earlier, I was told to check with intel support.
Basically, Dell optiplex 7040 that I have has Intel Q170 chipset under Socket LGA1151. I'm seeking help from Intel since rep from dell wasn't able to give me an answer since as per the rep, it was under intel's chipset and processor.
You were told incorrectly. Only DELL can tell you what their bios supports. If you cannot get that answer from them, then there is no need to go forward.
You must pass the BIOS hurdle first.