The serial numbers required for activation are dependent on the type of communicator that you have installed in the system. These characters can be found somewhere located on your communicator.
Here is a simple guide for most communicators:
M2M
This will be a 6-7 digit serial number located under the barcode on one of the 2 main faces of the device.
Honeywell
Here you will be looking for a Mac & Crc located in on the inside case of the communicator. Usually on a white sticker, with the Crc number typically located directly to the right of the Mac address.
ADC (Alarm.com)
With an Alarm.com communicator you will be searching for a 15 digit serial number also located in the communicators casing on a white sticker and it will need to say "IMEI:" preceding the numbers
Alula
Here you will be looking for a Mac & Crc located in on the inside case of the communicator. Usually on a white sticker, with the Crc number typically located directly to the right of the Mac address.