You can easily find your iPhone serial number (S/N), International Mobile Equipment Identity (IMEI) number, and identifier or ICCID. Follow these steps to get this information:
If your iPhone is functioning properly:
1. Navigate to Settings -> General -> About
2. Scroll down
3. The Serial Number, IMEI and ICCID are listed along with other information.
If your iPhone will not turn on or boot properly:
Your serial number and IMEI are both printed on the barcode label that's affixed to your iPhone packaging.
If you don't have your iPhone packaging: