Hi,
May I know if the original 2008 R2 server is also our licensing server, and we will migrate the licensing server from 2008 R2 to 2016?
If so, please refer to below article for RDS CALs migration.
Migrate your Remote Desktop Services Client Access Licenses (RDS CALs)
https://learn.microsoft.com/en-us/windows-server/remote/remote-desktop-services/migrate-rds-cals
Meanwhile, if you also would like to know more about the RDS deployment migration. You could take below as a reference.
Migrate your Remote Desktop Services deployment to Windows Server 2016
https://learn.microsoft.com/en-us/windows-server/remote/remote-desktop-services/migrate-rds-role-services
Hope the information helps. If there is any further question, please feel free to contact us.
Thanks,
Eleven