When exported from iWeb, it simply creates HTML files that may be modified in any way you like. Unfortunately, there is no easy way to simply convert it to a WordPress site and would require quite a bit of custom code.
My best recommendation would be to simply re-create the site using WordPress. There may also be a developer out there that would be able to create a WordPress theme based on the HTML output but iWeb.
My best recommendation would be to simply re-create the site using WordPress. There may also be a developer out there that would be able to create a WordPress theme based on the HTML output but iWeb.