The connection points are indexed in the prefix index under Hardware / Serial Port / Kindle Paperwhite.
To save you the clicks:
https://www.mobileread.com/forums/sho...d.php?t=195769
It is a LV (low voltage) serial connection (1.8 volt).
Communications parameters are: 115200, 8n1
I recommend the LV serial to USB adapter cable documented in the links of this thread starter post:
https://www.mobileread.com/forums/sho...d.php?t=170566