Code and ground question

[Elvis' jeep]

Have a P0306 (misfire on cylinder 6) code. Chasing down what it could be. My 2 questions:

Is the code for cylinder 6 or #6 in the firing order (which would be 4)?

Ground straps - how many and where?

Thank you in advance for your help

 

[Boinked]

Cylinder #6.

I could not even say how many grounds.