6.38 to 7.0 breaks after disabling of modules

I have a very large and very custom Drupal 6.38 site and am in desperate need to upgrade it to 7.
So I followed the instructions….

Back up
Set to maintenance mode
change to Garland theme
Disable all modules but not core or optional core (I also left UC_Core)
Then I got a broken page, unable to load or 500 error or something like page does not exist
I moved all Drupal 7 files and folders over but not the SITES folder and still, nothing

Please please help!


Drupal version: 

Source: https://www.drupal.org/taxonomy/term/21/feed