How do I move content from one field to another?
Let's consider that your content type is article and existing field is field_old and new field is field_new. Then you can use the script at once to copy all the data from old field to new field. 

$article_nodes = node_load_multiple(array(), array('type' =&gt; 'article'));
foreach ($article_nodes as $article_node) {
  $article_node-&gt;field_new = $article_node-&gt;field_old;
  field_attach_update('node', $article_node);
}


Am not sure, if this is what you are looking for.