Locked out of my iphone 8 how do you get your serial number?

What do you hope to do with the serial number of your locked iPhone? Why is phone locked? Did you forget your Passcode? Your Apple ID or Apple ID Password?

If you forgot your passcode, you erase the phone using your home computer with iTunes. This link explains how --> If you forgot the passcode for your iPhone, iPad, or iPod touch, or your device is disabled - Apple Support

If your phone is locked for another reason, please explain.

hello, you can look on your phone box: in the back, on the bottom.

I think you can find it on the back of your phone too.

hope I've been helpful

emma