Importing custom post types

Hi
I a building a new version of a site for a client from the ground up, to replace their old site. On their existing site the developers have made a post type named “work” and there are many postings on this post type which need to be imported to the new site. I want to bring them into the new site as posts, but I have not found a way of doing this. When I import the XML nothing happens.To avoid changing them one by one in the code can anyone tell me what part of the XML I should change in order to import the old posts into the new site please?

Thanks