The .JWPub file format is used exclusively by Jehovah's Witnesses within the JW Library app. While this format works perfectly inside the app, it is proprietary and cannot be opened by standard e-readers like Amazon Kindle, Apple Books, or Kobo.
You download the script, feed it the .jwpub file, and the script reads the internal SQLite database to output a clean .epub file. jwpub to epub converter 2021
That being said, if you still want to try online conversion tools, you can search for "JWPub to EPUB converter" and explore the available options. or Kobo. You download the script