My iPhone has been stolen

You cannot locate an iPhone using serial or IMEI number.

Tips here => If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support

Ignitestap Said:

"My iPhone has been stolen: My iPhone has been stolen. Please can you help me find the location. The serial number is FN***RXK"

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Was Find My enabled? If so, go here: https://www.apple.com/icloud/find-my/