Find my iPhone

Were they were sharing their location with using Find My Friends? Your friend could sign into icloud.com/find on the web or use the Find My app on another Apple device.

Set up and use Find My Friends - Apple Support

If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support

See my (correct) answer above.https://discussions.apple.com/thread/251164246?answerId=252221316022#252221316022

Go to the Find My app. Tap on “Me”. Scroll down and tap “Help a Friend”. Have your friend log in with their Apple ID and passcode.

Yes you can but the app is now called Find My, they are no longer separate apps.

DerekCarella Said:

"Find my iPhone:[...] How could I find my friends iPhone from my iPhone"

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Dial it, and see if it rings.