@alika if your site has any consistency in its structure you should be able to write a script to import it into the database rather than do it manually. I have done it in the past.
You could also write a script to change the HTML.
You say you are not a developer, but you could probably hire one at a reasonable rate as this is not a huge job - much cheaper than manually moving 10,000 pages.
Why do you need to change the taxonomy of the site? Unless the new structure offers a real improvement, you should retain what you have. Can you move to a CMS now, but change the structure later