I am adding a new electrical service to an existing one in the city of chicago. And was asked that I have to add a 400 amps with multiple meters, however I will need only 200 amps metered for my service. I need to show a one line diagram for the inpector.
Any help!

At this site you can see a sample of a oneline, and download a free demonstration and free trial that you can make your own, based on the system you have or need.

One-line Riser Diagrams - Electrical Software - Design Master

And a sample riser diagram of a simple residential service, you can see the detail that is needed.