lost work i phone. how can i track it ?

The only way to track the device is through iCloud and Find My iPhone. All of the following needs to be in place for it to work. First, Find My iPhone has to have been activated before the device was lost. The device needs to be powered on. The device needs to be connected to the internet. Then you can log into www.icloud.com from any computer and log in and track the device. If any of the above are not present, then you cannot track the device.

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