Hi There
Here's what I would do;
1. Set up the new WordPress site exactly how you want it to appear. Use the best URL structure that makes sense - don't worry about what it was on the old site. In most cases, the way WordPress does it with parent pages is totally fine.
2. In excel - make a column all the pages on your old web site - you can use Screaming Frog to crawl the site and do this. Then, in the next column, match the old pages with the corresponding new pages from the WordPress site. The URLs are going to be different but that's ok.
3. Last step - when you make the new WordPress site live, you just need to 301 redirect the old URLs from Dreamweaver to the new one for WordPress. A 301 redirect is something that directs users to the new updated page. You can do a 301 redirect with the Redirection plugin for wordpress.
What you end up with, is a new site with new URLs for each page - but the old pages get redirected to the correct new ones.
Hopefully that makes sense? And very sorry this question was not picked up sooner!
-Dan