How to get the IMEI code on a lost iPhone

Read the bottom section of Find the serial number or IMEI on your iPhone, iPad, or iPod touch - Apple Support

If you don't have your device

There are several places to check that might show the serial or IMEI/MEID number.

1. Go to appleid.apple.com in a web browser.
2. Sign in with the Apple ID that you use on your device. 
3. Choose the Devices section. To see the serial and IMEI/MEID number, select the device.

If you still need help, here's what to try next:

• Do you have a different device with iOS 10.3 or later that's
• signed in to your Apple ID? On that device, go to Settings > [Your
• name]. Scroll down to see any devices signed in with your Apple ID. To
• view the serial and IMEI/MEID number, tap the device name.
• Do you still have your device's original package? Find the serial number and IMEI/MEID on the barcode:
• 
  
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• Still can't find the number that you need? Contact Apple Support by selecting your device from this list:
  • iPhone
  • iPad
  • iPod touch
•