Hello @PSa-1463 ,
Myadmin is only accessible for Geotab Resellers, if you are a Geotab Reseller and you are not able to access it, please get in touch with your Geotab Partner Account Manager.
In order to get data from multiple MyG databases you can use MyGeotab API to access each database independently and get the data you need.
Take a look at this discussion: https://community.geotab.com/s/question/0D52J00008DvkDnSAJ/how-to-get-the-data-from-multiple-mygeotab-databases-into-one-centralized-location
Another option you have is Extendable Services - Extendable Services is a secured data-sharing technology that allows users to collaborate with trusted business partners by extending their telematics data to other Fleet Management Application users. For example, users can extend safety and performance-driven data to insurance providers to save on coverage, or extend engine diagnostic data with maintenance providers to save on repairs.
Hope this helps!
Best,
Ron