Hello,
Unfortunatly a 3.3.3 backup can only be restored to a 3.3.3 ACS.
To get the database up to 4.1 you will have to install ACS 3.3.3, import the database, then upgrade
the ACS software to 4.1. The softwate upgrade will also upgrade the database.
You can install ACS 3.3.3 on another server, upgrade the database then import the upgraded database
into your current 4.1 build if you don't want to uninstall your currently 4.1 install.
--Jesse