Moving registered users from mailpoet to Users

Hi,

First Let me explain, I had to open the topic again because I couldn't respond to Vaughan. For some reason there is no reply button.
I did check the options in membership and the box: "assign first subscription to existing users is checked"
but still my 30000 mailing list subscribers are not showing up.

maybe they need to be added as "users" first then they will automatically be assigned.

so how do i move them to being "users"

thanks

Aurora