How can I find my lost iPhone through the serial number

The Find My system doesn’t work by serial number, but instead by registered devices for an Apple ID account, that have had their Find My function activated. If Find My wasn’t activated, then it can’t be traced that way. If the iPhone is registered with a different Apple ID than what you have the credentials for, then it can’t be traced that way.

How can I find my iPhone 12 pro Max by using serial number

You can’t. Start here: If your iPhone or iPad is lost or stolen - Apple Support

If you do not have a secondary Apple device with Find My, then try accessing Find My on the web at: Find devices - iCloud.com, sign in there with your Apple ID account, same as for the lost iPhone.

As was stated over 5 months ago in the very first response in this thread, you can’t.

Can you help me to track serial number

No. It is not possible to track it by the serial number.