Script below (by LucD) will list all vm in each folder if you want to report for individual folders use "findstr" on the end of script:
$report = @()
Get-Folder | foreach-object {
$folder = $_.Name
$_ | Get-VM | foreach-object {
$row = "" | select FolderName, VMName
$row.FolderName = $folder
$row.VMName = $_.Name
$report += $row
}
}
$report | findstr foldername