Find iPhone if find my phone is not turned on

See the following from If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support

(that link has suggestions of other things to do such as changing passwords)

Find My [device] is the only way that you can track or locate a lost or missing device. If Find My [device] isn't enabled on your device before it goes missing, there's no other Apple service that can find, track, or flag your device for you.