Where to Report IMEI to Stolen iPhone?

Please note: Immediately after my iPhone was stolen, I did EVERYTHING that's been suggested on Apple support and here, on the Community Forum.

I have seen where people say they looked up the IMEI to check whether or not it's been stolen. That brings me to my question:

Where do people "report" the IMEI for the stolen phone??

PLEASE, I ONLY need this question answered; while people may mean well, I do not need suggestions for what to do when my iPhone has been stolen/lost, or for what to do with my account on iCloud. I have done all these things. Before I delete the device from my account, the last thing I want to find out is where, if anywhere, can someone report the IMEI for the stolen phone. Thanks!