Use the database manager with an SQL statement like this to grab all of the data for all users. Change the field numbers appropriately.
PHP Code:
$usersfielddata=$vbulletin->db->query_read("
SELECT field5, field7
FROM ".TABLE_PREFIX."userfield
WHERE field5 != '' AND field7 !='' ");
while($data=$vbulletin->db->fetch_array($usersfielddata)){
//DO Something with the data
}