If you are trying to set this up on an Item Count basis, then you would want to clone the files:
/includes/modules/shipping/item.php
/includes/languages/english/modules/shipping/item.php

Have you tried a search on:
clone item

this should give you details on how to clone the Item Rate item shipping module to make 3 separate shipping methods and then you can change the language files to read as you need them to ...