How to migrate Webform data from Drupal 6 to Drupal 7?
You can migrate Drupal 6 webform data to 7 using the Mirgrate Webform module. 


  It will migrate all nodes of the webform node type (with the default D6 fields using migrate_d2d backend), all the configuration* of the webform's settings, the form components, email destinations, submissions and associated submission data, in addition to any validation configuration you have (from webform_validation module). It grabs the "last downloaded" data too, in case your users were downloading sequential batches since the last time they were on the site.