I’d like to take progress that I have from a previous Anking v12 deck and merge it onto the anki step deck that is connected to the hub
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Hello,
That should be entirely possible. 
Folks upgrade all the time, and the process is designed with that in mind, so it should be straightforward and simple. The short version is that upon installing the AnkiHub version of the AnKing Step Deck, Anki will ‘check’ all of your cards and preserve any existing review history automaticaly.
This is by design, for all the reasons you might imagine, since folks understandably would like to upgrade without having to make a trade-off for what might be months, or years, of review history.
Please let me know if you have any other specific questions, or if there is anything else I can help with. Happy to answer any other questions or concerns you might have, and/or to help out however I might.