i hope you mean this:
$from = Get-Folder -Name "Datencenter"
$to = Get-Datacenter -name "testsystem"
$tgtAlarm = "Testalarm"
$alarms = (Get-AlarmDefinition -name "Neuer Alarm").extensiondata.moref
$alarms | % {
Move-Alarm -Alarm $alarm -To $to.ExtensionData -DeleteOriginal:$false
}
"Datencenter" for a german powercli/vSphere Client/ vcenter - root dir