The digital sets should automatically come with when you upgrade/migrate a server. The way the digital tags store data in PI Data Archive has not changed. How does your data look when viewed from PI-SMT?
As Jinmo Yi mentioned, the way digital tags are stored has not changed. Can you provide more information on this Mtell application? What data access method is it using to pull data? (AFSDK, PISDK, etc) Are you seeing any errors on the client application side or in the PI Data Archive logs when attempting to query the data? We will need some more information to figure out what might be going on.