You can find your QardioCore serial number on:
1) On the bottom of your QardioCore box, as shown in the photo here:
2) In the Qardio App:
Open the Qardio App to the QardioCore section. Tap on Settings in the bottom right corner and go to the QardioCore Settings screen.
*Please note: the QardioCore serial number will only appear in the Qardio App after you have successfully paired the device with your Qardio App.