So you just got started in your brand new hub and you notice that the quizzes you created before you were part of your hub are gone! Worry not, they are still there! Check out this gif to see how to move them into your hub so you can use all your great new features on them!
Additionally, you can use the same method to move quizzes into different parts of your hub, as seen here: Moving Content Between Hubs
Find more information on Hubs here: Hub Overview Page