I updated metadata in Calibre, but books aren't updated on Ipad

I use Windows 10 to run the latest Calibre, and my Ipad 5th generation to run Marvin 3.

I have successfully edited the metadata in 400 books in Calibre, I copied the epub book files from the Calibre library on my PC, and pasted them into my Itunes file sharing space for the Marvin 3. I synced the updated books to Marvin, but none of the metadata on the books has updated.

What am I doing wrong? How can I get updated metadata?

Thank you very much for your help!