This seems contradicting to me!
The project page of emfield states:
FileField does not need a Drupal 7 version because it has been moved to Drupal Core! To upgrade FileField to Drupal 7, install the Drupal 7 CCK Package and use the Content Migrate to upgrade FileField to Drupal 7.
On the other side, the CCK "Migrate fields" assistant contradictingly reports:
Field type: filefield
Content type(s): Text Plus, Text Plus Inline, Video
Other info: Missing field module: 'filefield'. This field cannot be migrated.