Trying to bulk restore my library, need help with tricks

[Bolognie1]

I have a bunch of books, around 300 I think. They were all in my library, and after the grueling process of cleaning them up, before I could back it up I accidentally erased all metadata somehow. Either that or I copied duplicates to my ereader and accidentally deleted all of them from my library instead of the device after smart-eject, I can't remember.

Anyway, I have a huge mess of EPUB/ MOBI/ PDF/ AZW files in a bunch of subdirectories where I got most of them from in the first place after compiling all the ebooks I own. I managed to recover quite a few from my device, from a previous back-up, from the recycle bin etc.

I am now at the stage where I more or less have the entire thing recovered, all formatted nicely, all converted to the formats I want, but I am not sure if I have all of them. It isn't too big a deal as I won't be reading everything any time soon, and anything I want to read that isn't there can easily be rectified, but my OCD is getting the better of me...

Is there any way I can even say, find some rough number of books from the old library somehow? Or can I scan this entire mess of subdirectories for a rough number of "epub" files or something? It is kinda annoying as I'd like to have all the originals formatted correctly incase I come across some kind of conversion artefacts...