It all depends how much appstore module you are using because you need to upgrade all those modules. And it is dependent on the amount of consistency errors you will find in your database. See also the documentation here: https://docs.mendix.com/refguide/moving-from-6-to-7#4-1-stateless-runtime
You can do a test migration and I would suggest to move to 7.22.2 (7.23 is on it's way). To do a test migration make sure you have everything commited to the teamserver. Then open the Mx7 modeler and open that project and try starting it. If you run into trouble the forum is here to the rescue :)
Good luck,
Ronald