Any idea how I can switch paid members from DAP to membership/prosites?

I have a site using Digital Access Pass (DAP) with a few hundred members-some paid, at different monthly prices, several free.

Do you know of a way to migrate those users to your membership/pro sites systems? Without those paid members having to complete the checkout process again?

I really want to switch, but I don't want to lose my paid members.

Suggestions?