Decommission Exchange 2010 on Premise server

Try to run the following powershell on premise server and Exchange online. Both of them doesn't work and it says 'Remove-Organization' is not recognized as the name of a cmdlet...  Can I remove it in the  console and web interface. I see it under Exchange Console > Organization Configuration.  Do I also need to remove Federation Trust ? Thx

onPremise :
Remove-Organization Relationship –Identity “ On Premises to Exchange Online Organization Relationship”
 
Exchange Online
Remove-Organization Relationship –Identity “ Exchange Online Organization Relationship to On Premises”