After you Demo Migration is done go to the back-end of the site to check results.
Go to http://your_drupal_site_url/?q=user/login
In case you migrated data to CMS2CMS preview site use login: testuser , password: testuser to enter admin panel.
If you moved data to your own website, use your access credentials.
Use this list to check results:
Content pages
Menus
Categories
Users
After the whole content was checked, complete the migration.