If your charge point looks like this, you have a MyEnergi Zappi:
We'll need two serial numbers if you have a Zappi installed.
The one on the Zappi charge point itself (the unit on the wall outside your house), and also the on the bottom of your Hub (your hub will be indoors, usually close to your Wifi router).
Your hub will look something like this:
In both cases, the serial number is usually on the bottom of the unit.
If you're struggling to find the serial number on the Zappi, you can always find it in the Information section of the menu on the LCD screen of the Zappi: