The latest release version is 3.53 and the latest beta version is 3.54...both have specific requirements - and the versions are vastly different coming from 2.0 versions. It is NOT as simple as just uploading with a single revision.
I'd recommend downloading them and before changing anything on your hosting packages review the following files (which are attached to each version). Of course ALWAYS make a full backup and have a backup plan in case it doesn't go as expected.
The files you need to review and understand are:
- how to upgrade from v2.txt
- how to install.txt
- how to upgrade from v3.08 (mysql to mysqli).txt
- how to upgrade.txt
If you do not understand the process well then I would recommend getting some additional help and also consider getting consulting support directly from the Interactive Tools team. It's worth the price and will be seamless while avoiding catastrophe.