To Update Or Not To Update!
 

I downloaded Kubuntu 16.04 when theres Kubuntu 14.04 in my laptop, because I had a problem booting it, and I had to fix it with a Live USB.

I think I downloaded the wrong version, but I sort of liked it. I reached my hard drive files with Kubuntu 16.04 from my USB Drive, and I wonder...

If I install it from my USB, will it update Kubuntu from 14.04 to 16.04, and the files will be intact? Or everything will be formatted and gone?

In the absence of additional information, I must say the odds are that it will overwrite your current install.

You probably should take a look at this: http://www.ubuntu.com/download/desktop/upgrade

In any event, when you look to upgrade an install, you should back up your current data as if you were reinstalling from scratch, because there is always the chance that something might go wrong. For an extreme example, someone might drive into a light pole causing a power failure in mid-upgrade.

Stuff happens--prepare for the worst and hope for the best.