Apple doesn't get involved in lost or stolen devices. All you can do is report it to the local police and use the Find My app to try to track it. Here is a link which explains what to do if your phone is stolen --> If your iPhone or iPad was stolen - Apple Support
Thieves are smart. They usually place a stolen phone in a Faraday Bag to make it impossible to track. Even if you did see its location, you should NEVER attempt to go where it shows on a map. It could be very dangerous and life-ending. Let the police know, if you are able to see its location.
And be advised that if you get any message which appears to come from Apple, suggesting your phone has been found and all you need to do is provide your account credentials to confirm it's your phone, that message is NOT from Apple. It is from the thieves, who are hoping you'll be dumb enough to give them your credentials, so they can wipe the phone and sell it or use it. DON'T fall for this.
Finally, contact your carrier and ask them to Blacklist the phone, so it can't be activated on any other carriers network.