Does the VM has applications/databases, like Exchange or SQL Server databases that you want to back up? If so, you would need an Agent for Application and Databases licence for each application/database on the VM. With this licence, you also get an Agent for Windows System which allows you to backup the files on the VM. You would need to backup this VM as if it is a physical machine. To recover this VM, you would need to to recover it as if it is a physical machine.
If you want to backup and restore this VM as a VM, then you need either an 'Agent for VMware and Hyper-V' licence or a V-Ray Edition licence. The advantage of a V-Ray licence is that it gives you an unlimited number of Agent for Application and Databases licences to backup applications/databases. The V-Ray edition is usually good for an environment with lots of VM.
If you get an 'Agent for VMware and Hyper-V' licence, then you still need to buy Agent for Application and Databases licences to backup applications/databases in your VM's.
Before buying any licence, check with the Symantec Licencing department which is the final authority on licencing.