Migrate to node content type with the right user id (migrate module)
You use the sourceMigration() method of the migrate module. You should:

1) Write one migration to migrate old users to the new version of drupal.
2) Then write a migration that moves an old table to the new version of drupal.

In (2) when you setup your field migration it sounds like you've written:

# Field Mappings Docs: https://www.drupal.org/node/1133448
# this maps new &lt;= old field.
$this-&gt;addFieldMapping('new_user_id_field', 'old_user_id_field');


When you want to write:

# Search for sourceMigration on this page:
# https://www.drupal.org/node/1133448
$this-&gt;addFieldMapping('new_user_id_field', 'old_user_id_field')-&gt;sourceMigration('MigrateLegacyUsers');


This then uses a previously run MigrateLegacyUsers migration I described in (1) as the lookup for the new user ID in the new drupal site from the mapping table stored by Migrate for the old_user_id_field created during the MigrateLegacyUsers migration task.

Also note if you possibly have multiple users migrated into the system, say from a drupal legacy system, a wordpress system or LDAP you could write:

`-&gt;sourceMigration(array('MigrateLegacyUsers', 'MigrateWordressUsers', 'MigrateLDAPUsers'));`


This means: Find the legacy user id among all these possible prior migrations of Users. The first user_id that matches the requested legacy ID will be used by migrate (so be careful to assure all the user_ids are unique across multiple sources).