@EHacking  

This may be a question more suited for the VMware community, but I would try something along the lines of

1. Use PowerShell or another scripting language to connect to the vSphere API to retrieve information about the virtual machines as the virtual desktops are essentially virtual machines in this context.
2. Identify and filter the virtual machines that correspond to your virtual desktops. You might have specific attributes or tags assigned to these machines that distinguish them as virtual desktops.
3. Count the number of virtual desktops based on the filtered list obtained in the previous step.

Thanks,