I cant find my kernel number anywhere First off I'm not very experienced with phones, but while trying to root my phone I need the kernel number.  I've looked where the instructions told me to look, in my about phone section. Under the kernel version it only says:

3.0.31-980103
se.infra@sep-129 #3
smp preempt fri mar 1 04 29 20 kst 2013


Second, I've downloaded the update to 4.1.2. (I think ice cream sandwich or jelly bean.)  My model number is sch-r760x.  I have an Alltel wireless.

I just want to root my phone.  I don't want to spend forever looking for this "kernel version".
That is your kernel version.  Specifically, you are running version 3.0.31 of the Linux kernel.

The rest of the line is various details about who compiled it, what options were set, and when it was compiled.