Android has its own hierarchy of storage and under that is stored the hierarchy of books that is dependent on which library/reader you use.
For me, all my books are just in /sdcard/Books (with no subdirectories).
Settings are all a bit scattered because the Poke3 is using custom Onyx Settings and not the Android normal Settings. If you run a different launcher (as I do) you can access the regular Settings.
The manual for the Poke3 is here:
https://drive.google.com/file/d/1C6j...Ge77VPEMw/view
(Found from boox.com > Support > Downloads > Poke3 > Manual)
I guess that you are copying over books with a USB cable using Windows File Explorer?
Or are you using Calibre or something?