Can someone please tell me where the orifice tube goes in a 1985 deville

Welcome to AF.

Find the biggest, meanest-looking truck driver you can on the highway, then cut in front of him and flip him off - he'll tell you where the tube goes. :)

Seriously, I am not sure what you mean by 'orifice tube'. Cars have many orifices and with related tubes. I have never heard that expression before, but if you give us more details, we may be able to help.