+1 (especially the ALF part)
K for PC will show you a list/covers of books
available on your account.
double clicking those downloads just those (a PULL vs the PUSH Itimpi outlined)
Books will be in the My Kindle content folder and WILL NOT have a clear title visible. Adding to Calibre will extract the proper title as part of the process.
I drag and Drop or copy to the Auto Add folder (you configured).

COPY, not move from My Kindle Content
Normally, you only add (to Calibre) those WITH format extensions (AZW*, Mobi)