You can probably find most of what you need in the firmware upgrades which are freely available from PocketBook. They contain images of most of the partitions. It will give you an idea of what you are up against. There is a thread about replacing the SD card in some models which you would probably find useful (
https://www.mobileread.com/forums/sh...d.php?t=278728). There is some copy protection in place that the thread goes into. One snag I can think of is that your device does not have a PocketBook serial number and I'm not sure what you should do about that.