Reading a Metadata.db file

I'm trying to read a metadata file, but Calibre won't open it as metadata.

It imports it as a book and when you try and open the book in the viewer I get the following error:

calibre, version 3.26.0
ERROR: Could not open e-book: Failed to read book, /Users/Shared/Maddy's Calibre/eBooks/Unknown/metadata (4963)/metadata - Unknown.db click "Show Details" for more information

Traceback (most recent call last):
File "site-packages/calibre/utils/ipc/simple_worker.py", line 284, in main
File "site-packages/calibre/ebooks/oeb/iterator/book.py", line 55, in extract_book
File "site-packages/calibre/ebooks/conversion/plumber.py", line 752, in __init__
ValueError: No plugin to handle input format: db

Can someone talk me through accessing the file? It's a list of books from the Baen Free Library which I want to check against some of my old ebook files from Baen.