Need help importing/exporting confirmed subscribers (not leads or customers)

Site URL: http://www.1924.us

In transferring a new website from 7.0 to 7.1 we are running into an email marketing issue: We have 20,000 customers who are not subscribed, and 10,000 customers who are, when I try to export it exports all of them and in no way sorts them, so how do we use Squarespace's newsletter management effectively if we cannot accurately import customers to the new site?