Add post attachment images their links

I have a website with alot of pictures as attachment in the posts, but i decided to use lightbox in the future. I have a big problem as of now none of them was imported as a file so they dont have the source url which is needed by all of the lightbox plugins that i found. Is it somehow possible to do this automatically as if not i gotta spend maybe a month doing it manually. In some posts i have more than 10 images… :/