To get all the cards in V12, do this:
Please try resetting your local changes. To do this:
Go to browse in your Anki → at the top click on ankihub addon tab → press reset all local changes
This will restore everything to what AnkiHub has unless you have specifically protected those fields
After that, see these posts:
To remove V11 tags: Why do I still have V11 tags in V12?
To remove V11 cards that were not brought over to V12: How do I delete all V11 cards after I have upgraded to V12?