[Ptaker]

Three months ago I moved 8 Calibre libraries from a windows 7 computer to a new windows 10 computer. Now I discovered only one new library had over 600 books with NO format.

FACTS:
Moved 8 old libraries from a Windows 7 computer (using Calibre 3.48) to a new windows 10 computer using Calibre 5.14 program. I did a library check before the move and it had no problems. Also, all of the old libraries had no blank format books. I did a check on the new computer and it had no errors or problems.

Three months after the conversion, on the new computer, I discovered there were over 600 books that had no format in only on one library. I seem to remember a problem with the conversion in that library but thought I solved the problem (whatever that was). I did a library check then and now on the new problem library and there were no problems found. On that library my old library's latest date was January 24, 2021 while my new library has the April 10, 2021 date due to added items.

FORMATS USED: I usually add books to the library with only epub, mobi, html, htm, lit and azw3 formats and convert them to my kindles to either mobi or azw3 formats.

REQUEST: How to I get one problem library corrected?

QUESTIONS: Can I export only the one old library and import it into the new computer? If so, how do I get the "duplicates" of those without formats replaced, while not adding duplicates of those books whose formats are correct? We are dealing with over 600 books without formats and over 1200 books with correct formats as of January 24, 2021. Also, I have added books to that library since that date too.

I hope I provided all the information you need to hopefully provide a detailed easy solution to this confusing problem.