The IP base feature set is already included in your the IOS image currently installed in your switch. You need to purchase the software license for the IP Base set from your reseller or Cisco partner. That means that you don't have to buy a new switch.
This document might help:
http://ciscorouterswitch.over-blog.com/2015/08/licensing-on-cisco-2960-3560-3750-series.html
