The file you have downloaded will only work for recovery after either 4.0 or 4.1 has been loaded on your sensor. There is special code in the 4.0 and 4.1 to be able to use a recovery partition, that is not in the 3.x versions.
It can not be used to upgrade from 3.0 or 3.1 to 4.0 or 4.1.
To upgrade to 4.1 you will need to get the 4.1 CD.
If you have kept up with the SmartNET maintenance contract on your sensor then you can use the Product Update Tool on CCO to order the upgrade CD for no additional cost.
If you have not kept up your maintenance contract then you will either have to contact your sales representative and see about re-initiating your contract, or purchase the CD (if I remember right the CD IDS-SW-K9-U costs $5,700).