Apple company world please where imei number my phone iPhone xsmax please help

You can find this information by going into Settings > General > About on your device, it may also be printed on your purchase invoice.

Find the serial number or IMEI on your iPhone, iPad, or iPod touch

As explained in the support document you posted from ,

IMEI number can be found in Settings->General->About->IMEI if you have access to the iPhone.

Otherwise, it is printed on the back of the sim tray.

Read the support document carefully please.

https://support.apple.com/en-us/HT204073

Guessing at what happened: If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support

If that has happened, then contact your carrier for assistance here, as they'll have the IMEI info.