I'm trying to migrate an old SBS 2012 Essentials to a new server - Step 16 in your migration guide uses PowerShell command that was introduced in 2012 R2. So the command doesn't exist in 2012. Any thoughts on an alternate way to back this up and restore it, please?
You may be able to use the GUI. In most case you really don't need to migrate the CA. Was the CA only used for the Essentials functionality or do you have some other need for it like Radius authentication?