Hi. Sorry for the late response, I think this was covered in a support ticket.

The proper way to do this is to 'link' each Dynamic Field you have within Dynamic Registration to a core DNN field (you can add new ones under Admin, User Accounts, Manage Profile Properties).

This creates on 'repository' of data that you can utilize and then import using IUI, Export, utilize with Dynamic Registration, Dynamic User Directory, and other 3rd party modules.

-Chad