How do I manually migrate a site? So far I copied all files to a new directory.

Put the site into Maintenance Mode

Then I downloaded the database and imported it into a new database I created.

Truncated the following tables in the database


cachetags
cache_*


Updated settings.php with new database name, database user and password.

Currently the problem I am having is that I where I moved it to has a different path. Before I had my Drupal site set up at /xyz/my_drupal_site and now I have it set to /abc/my_drupal_site. I believe at this point I just need to update the database with the new path and I am not sure what needs to be updated (a global replace did not seem like good idea) or if there is an admin page that I can go to to take care of it. 

I found instructions for Drupal 7 and they mentioned /admin/settings/file-system but it does not appear to exist in Drupal 8.

Also I want to make sure I am not missing anything else.
You likely don't need to change anything at all. Just move the folder and clear caches. Maybe you need to change the path in settings.php but only if you hardcoded it there before.

The instructions you found are for Drupal 6 and changing the path is no longer necessary unless you manually changed it to something else than the default location before.