Hello,
Here's some alternatives:
Getting a MyGeotab excel report:
To simplify, if you go to MyGeotab UI, then go to vehicles, click on Report button, you can select a report template and click to download an excel.
Then, unhide the tab "data" on the excel file. You will have there a row belonging to each vehicle on your database. Simply look at the DeviceName, ID and DeviceSerialNumber to get that master file relation between ID vs vehicles.
Concepts about IDs using MyGeotab SDK:
On the other hand, you can find some concept definitions on this link:
https://geotab.github.io/sdk/software/guides/concepts/#id
Generic concepts:
To identify a vehicle in MyGeotab, it is important to know that the data comes from a device (hardware) registered in a database.
When you add a device (a unique serial number of a physical GO device) into MyGeotab, then an ID is going to be generated automatically in that database. For user identification, it is needed to add a devicename (the identifier that is shown in most of the reports, including map view). DeviceName can be edited by the user, but the ID will never change.
With that in mind, if you look at Device object on the SDK, you will find that the ID is a property that can be queried
https://geotab.github.io/sdk/software/api/reference/#T:Geotab.Checkmate.ObjectModel.Device