importing XML file with drupal 6 nodes to drupal 7
You're best bet would be to download a views data export from drupal 7 and one from drupal 6 and find the difference (it is easiest if the drupal 7 and drupal 6 contain the same data). Then find a way to convert one to the other, either using PHP to transfer all the data into an array then output in the required format or maybe it's as easy as just a few small changes.

Sadly there is no views data export drupal 6 to drupal 7 conversation module.