S49 can only be applied to 4.1(1) sensors so you must first upgrade to 4.1(1) with the following package:
IDS-K9-min-4.1-1-S47.rpm.pkg
THen you can install the S49 Signature Update:
IDS-sig-4.1-1-S49.rpm.pkg
Both are available at:
http://www.cisco.com/cgi-bin/tablebuild.pl/ids4
The problem you are going to have is that the 4.1(1) upgrade package requires that the memmory in your IDS-4210 be increased.
If you have a SmartNET contract on your IDS-4210 then you can use Cisco's Product Upgrade Tool to order the memmory upgrade at no additional charge.
The 4.1(1) upgrade can not be loaded on an IDS-4210 without the memmory upgrade. So you can't load S49 without the memmory upgrade.