Every iphone has a unique identifier code, known as an IMEI number. The letters IMEI stand for International Mobile Station Equipment Identity, and the number is used to identify each mobile phone.
The IMEI number is used by your mobile phone company to match the phone to the networks, so it can figure out who is making calls. It is also used to maintain a blacklist of stolen mobile phones. In the UK a database is publicly maintained by a charity so stolen phones cannot be moved from one network to another.
Just try this steps to find out your imei
1.You can retrieve the iPhone's IMEI number by dialing the code *#06# into the dial pad.
2. Find out imei by looking back of your mobile
3. If Apple hasn't etched the IMEI on the back of the phone, you need to check the SIM tray.
4.The IMEI number is also located in the iPhone's Settings
5. Use itunes to display your located iphone's IMEI number
6. If mobile in Activation lock you can look your IMEI by tapping (i) on bottom of iphone's screen
