Get-HardDisk : Cannot process argument transformation on parameter 'Datastore'. Strings as pipeline input are not supported.

any idea why I am getting this error?

$VMs = get-content vms.txt

foreach ($VM in $VMs)

{

$VMDK = $VM | get-harddisk }

sk

Get-HardDisk : Cannot process argument transformation on parameter 'Datastore'. Strings as pipeline input are not supported.

At line:1 char:7

+ $VM | Get-HardDisk

+       ~~~~~~~~~~~~

    + CategoryInfo          : InvalidData: (xjzxbwg1105x:PSObject) [Get-HardDisk], ParameterBindingArgumentTransformationException

    + FullyQualifiedErrorId : ParameterArgumentTransformationError,VMware.VimAutomation.ViCore.Cmdlets.Commands.VirtualDevice.GetHardDisk