I don't know how to transfer ownership of a shared/collaborated folder. (I have a workaround though, that I describe at the end.)
But to learn who's the owner, you can go to your CC Files web space, click on a folder, and the little picture thumbnails appear across the top indicating who's a user in the folder and who's the owner. The owner appears first, and their name appears in a tooltip. Below is a CC Files folder that a client added me to. (I'm the 2nd thumbnail.)
Also if you go to Share/Collaborate any CC Library or Folder, whether or not you're the owner, the Share dialog box lists who's the owner and who are users (editing privileges or not). The owner can remove users, or even all users, but cannot remove themselves or assign Owner to anyone.
I think a solution though would be to ask whoever you want to be the new owner to go to the shared Folder/Library and choose Duplicate or Copy. Then you can remove all the users from your folder/library and they can add the same folks to the duped one that they now own.