transfering bought kepub from device to PC

I've bought a few epubs from the kobo website, but the last one was of poor quality, so I decided to get the kepub from the kobo desktop (a first for me). Apart from having to delve into the SQLite database again to drop duplicated shelves, and having to do a search to access it, I'm pleased to have a decent quality book to read (which should be a given with bought books but...). I want to save this original kepub version into Calibre, but I don't know where to look for it in the device - even choosing the show hidden files in windows. I know I saw the answer somewhere, but can't remember where.

Can anyone direct me to the appropriate post?

Thanks.

PS: I would also very much like to be able to get the original kepubs without having to sync my kobos and having to lose time editing the SQLite database.