How do I update kernel 3.3.7 to 4.7.9?

[winger9]

My system is Live Knoppix 7.0.2 and kernel 3.3.7 installed to hard disc.

Can I happily update kernel 3.3.7 to kernel 4.7.9, and if I do, will the rest of
my system carry on the same as before?

The reason I want to update the kernel is because I've bought a new Seagate 2Tb
usb hdd, and it won't work on my present system (it works fine in Windows 7).
My testing, failed fixes, and Internet trawling leads me to the conclusion that the kernel
probably contains a bug that is preventing the drive from working.

(The following link shows what the problem is:

http://knoppix.net/forum/threads/323...340#post135340 )

The reason I want to update specifically to kernel 4.7.9 is because the Seagate
drive works OK with Live Knoppix 7.7 on usb memory stick, which has kernel
4.7.9.

My humble questions:

Please could you tell me what steps I carry out in order to update to kernel 4.7.9.
I'm out of my depth here, so could you spell out each step please.

Where do I get kernel 4.7.9 from?

Do I need to backup first?

Also, how do I revert to kernel 3.3.7 if I need to?