Assumptions is that you as admin already uploaded the correct template. You can do import and export of templates as XML file with a module like this: https://marketplace.mendix.com/link/component/363 There are multiple in the appstore.
This way you control that the template with a specific name is there in the database.
Now in the microflow you can do a retrieve action of that template by the name you choose when you saved the template.
Does this help?
Regards,
Ronald
That helped a lot. Thank you!