I can't find my iPhone, what can I do?
Please help me find my other iPhone
[Re-Titled by Moderator]
Assuming that you enabled Find My on the phone.....before....it was lost, follow the steps in this Apple Support document to try to locate your phone.
Find your lost iPhone or iPad with Find My - Apple Support
Please remember though that the Phone will not show up on the Find My map if one or more of the following conditions exist:
The battery has run down
The phone has been powered off
The phone does not have an Internet connection where it is currently located
Unfortunately, there is nothing more that you can other than keep checking a few times each day to see if the status of the phone has changed.
Good luck