How can they make a movie out of The Wedding, since Noah and Allie died in the film version of The Notebook?

Movie magic, of course, if the producers choose to go that route. Either (a), Noah miraculously recovers -- in which case, the opening scene would be one in which Noah is rushed, via ambulance to the hospital, (b), make Noah more of an imaginary character that resides in Wilson's mind, and uses "memories" of conversations gone by identical to those in the book. (c) Set The Wedding earlier -- in other words, BEFORE the film version of The Notebook and create a new story for Noah that's different from the one in The Wedding, or (d) Delete Noah's character entirely.

All of those options, while not strictly in line with The Wedding, are typical of the way Hollywood would choose to handle the problem. If asked, my own choice would be for choice (a).