What file should I added is_new in it?

I want to maintain the same content ID drupal 6 to drupal 7, it needs to map that ID to the nid as well as setting the is_new field.
https://www.drupal.org/node/1349696

But I don't what which file and which line should I add the script,

It is added to the migrate_d2d\d7\node.inc ?