Go to Settings > General > About and look for your device's IMEI
Dial *#06# to get IMEI
Before trying anything else, you can try simply dialing *#06# on your iPhone (or any mobile phone), this should retrieve the IMEI number. Give it a moment and the IMEI will appear on the screen � this little number dial trick actually works to retrieve the IMEI on other cell phones too, not just the iPhone.
On back side of iPhone
The iPhone 5/5c/5s/6/6+ and the original iPhone have the IMEI number engraved on the back of the phone, near the bottom.
On SIM card tray
For find imie, you need remove sim card tray from device, and then you can find imei on it. (not on all models you can find imei via sim tray)