Thank you theducks.
1. Neither MacFinder nor Win+E does not find the files.
2. I installed it. I deleted the library. I am reading folders and sub-folders (for 179k books) since I did not find a ReRead source button.
3. I could not find what you are referring to
https://manual.calibre-ebook.com/faq.html.
I imagine you recommend setting the Calibre library where my source books are (DropBox in a task-oriented structure
https://johnnydecimal.com/).