File structure is the same for all PBs. If you use a WIN PC just omit the /mnt/ext1/ part and go to [DRIVE NAME]: Pocketbook912. There are all the folders. Etensions.cfg has to be created (or copied from any source here in this forum, just search).
For further questions on *.cbz I suggest to ask them in the respective thread and not here.
For keyboard questions there is an own thread to be searched, I only know what worked for me and this I told you.