The database version says:
SITE_APP_VERSION 5.6.3.1
SITE_INSTALLED_APP_VERSION 5.6.2.1
APP_VERSION_LATEST 5.6.3.1

my_site/concrete/config/version.php
$APP_VERSION = '5.6.1.2';

my_site/config/site.php
define('DIRNAME_APP_UPDATED', 'concrete5.6.3.1_updater');


I was reading this page:
http://www.concrete5.org/documentation/how-tos/developers/troublesh...

It says download the core files, and gives a URL but that link is invalid. Where exactly would I find the core files?. Here is the quote:

"The concrete5 core. These are the replaceable files located in (your_site_root)/concrete, or if you've upgraded in the past, (your_site_root)/updates/concrete5.x.x.x"

Which ones do I replace?
(your_site_root)/concrete
OR
(your_site_root)/updates/concrete5.x.x.x

How would I know if I've updated in the past?
Is it simply a matter of replacing the my_site/concrete folder with the latest version of it?