How to track stolen iPhone

Read: https://support.apple.com/en-us/HT201472

If Find My is not on, no hope. If yes, lock it or even erase it.

Do not reply to any "Apple Special Security" (or "police") messages asking you to click a link and confirm your AppleID password .. this will steal that password and fully control information on the device.

Did you have Find My iPhone enabled? Also, do not post your serial number in any forum. It is the equivalent of a SSN; personal info that should not be shared.