Script to find Number of VMs per data store in vCenter

Add-PSSnapin VMware.VimAutomation.Core   (For vSphere 5.5 or below)
Import-Module VMware.VimAutomation.Core  (For vSphere 6.0 and above) 
Connect-VIServer vCenterName

Get-Datastore | Select Name, @{N="NumberofVMs"; E={@($_ | Get-VM).count}} | Sort Name |Out-file "C:\Temp\VMcount.csv"