Check label attached to your Brother machine

The serial number is on the back of the unit.
 

Check the serial number from the machine's display

You can also see the serial number on the machine's display (hereinafter called LCD) following the instructions below:

1. Press (Settings). (This step might be skipped in some models.)
    
2. Press All Settings.
    
3. Swipe up or down, or press the Up or Down arrow key to display Machine Info. or Machine Information.
   Press Machine Info. or Machine Information.
4. Press Serial No..
   The LCD will display the machine's Serial Number.
    
5. Press (Home).