Hi DD,
I think you have to choose the first vm within your array of vms. So in your scriptabe task you can choose the first vm like this:
var vm = new new VcVirtualMachine() ;
vm = vms.shift(); // Returns the first item within the vms array
And then use vm to get the informations you want insted of vms.
If this is working. The error is, that you are trying to get the .config attribute from an array which only have the attribute length. Herefor you can take a look to the API explorer within orchestrator where you can see attributes and functions of objects like VcVirtualMachine or Array.
If this isn't, we have to see your code from the scriptable task to help you.
Regards,
Chris