Was already in the One Liners, but needed again. So slight variation.
After doing Connect-VIServer…
Get-VM | Where-Object {$_.PowerState -eq "PoweredOn"} | Get-CDDrive | Where-Object {$_.IsoPath -ne $null} | FT -AutoSize Parent, IsoPath
Or to export to csv
Get-VM | Where-Object {$_.PowerState -eq "PoweredOn"} | Get-CDDrive | Where-Object {$_.IsoPath -ne $null} | Select-Object -Property Parent, IsoPath | Export-Csv -Path .\iso-mounts.csv
Find connected CD-ROM on VMware via PowerCLI