how can i locate my lost phone

Use any internet browser and log into www.icloud.com/find

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

It doesn't matter what cellular plan your lost iPhone is on.

With the Find My app (also known as the Find My iPhone app in iOS 12 and earlier), you can locate your lost iPhone, iPad, Mac and more.

You can use an AirTag to find your lost object.

If you don't know how to use Find My, check out this videos: