Track someone’s iphone
How to track someone’s iphone in case of lost
iPhone 5s, iOS 12
Question marked as
Use any internet browser and log into www.icloud.com/find
More information and options in If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support
Note that Find My must be enabled on the device before it is lost (i.e., while you still have physical access to it). See: Set up Find My on your iPhone, Mac, AirPods, or other devices - Apple Support