My CPAP machine doesn't have a 3-digit code. Now what?

myAir supports all AirSenseTM 10 or AirCurveTM 10 machines with built-in wireless technology, where a supported wireless network is available. These machines all contain an 11-digit serial number and a 3-digit device number on the back of the machine.

How do I find the 3 digit device number to register my machine on MyAir