Why don't you update to the current (with TLS fixes), 3.4.2 and then jail break that?
The serial port of the K3 is on the lower, cover light, connector.
You can connect to it without opening the Kindle.
If you require a software only jail break, do not hold your breath, the author is gone from this site.
I am assuming you took the jb archive from:
https://www.mobileread.com/forums/sh...d.php?t=225030
Opened it.
Read the "README.txt" file (paying attention to the directions for people with firmware more recent than 3.2)
Followed those directions
And something did not work.
But since you did not say what you had tried and what the result was of each thing you tried, I have to assume you've already done your part.