my phone is lost , i have no imei no: , how i got it ?

From your box, or if you have a backup done through iTunes: iTunes>Preferences>Devices...hover your mouse pointer over the name of your backup, a popup will appear showing SN & IMEI number.

If you have not enabled "Find My iPhone" in the lost phone's settings, you cannot trace it. Tell the carrier, the police, the insurance company, and change any compromised passwords.