Can I get IDs for message templates?

A message template does not have an ID. Rather, companies can create a message template name, like "online_invoice" or "payment_receipt". 

A name for message templates can only contain lowercase alphanumeric characters and underscores ( _ ). No other characters or white space are allowed.

When creating your message template, you can already specify the name. For your reference, each message template you create is referenced in your Facebook Business Manager.