How to find lost iPhone?

Find your lost iPhone or iPad with Find My - Apple Support

This will only work if you had Find My enabled on the iPhone before you lost it. The main Find My mechanism relies on the phone having a connection to the Internet, so if it is turned off or doesn't have a connection, there might not be a location fix.

Be careful about personal safety. If you think the phone has fallen into the hands of criminals, and you get a fix on the location of the phone, you might not want to go to a place where criminals gather.

Beware messages from "Apple Security" or "Apple Support" or the like, claiming that they have found your iPhone. These are not from Apple, but from criminals who want your assistance in removing an Activation Lock (so they can "make your phone their own") or in defrauding you in other ways.

This may help --> Do's and Don'ts for lost iPhones - Switch… - Apple Community