Importing Listings from Older Version to Newer Version

We’re running an old version of the DirectoryPress theme, and are upgrading to the new responsive theme. I’m building the site on a development server, and trying to import all the old site data is giving me trouble. When I import the posts from the old version, they show up as blog posts, not listings. Is there a way to do this easily? We have over 1,000 listings — I cannot do this manually!

Thanks!