Fatal error: require_once()
It means that the file admin.inc (part of the Views project) is not found.

This file is supposed to be on the following path below your Drupal root sites/all/modules/views/includes/.  If you check, I'm sure that you'll find that it is no longer there.

Why this happens is more difficult to say.  I presume that you had the Views module installed on your site in sites/all/modules/views/ as indicated by the path (for the record: this is the right place), but that after the upgrade, it is no longer there?  Again, please check?

When upgrading, the sites subdirectory from the pre-upgrade site is supposed to be the sites subdirectory in the upgraded site.  If this, for some reason, in not the case, the contributed modules you've installed (such as Views) will be lost.

Please check if the files are missing (as I belive they are).  If they are missing, the solution is to make sure that the entire sites subdirectory hierarchy is properly moved into the upgraded site file hierarchy.