The change of file format occurred in newer versions. Unfortunately there is no way to import data from versions 2.x into 3.x as most data structures have changed significantly when the product was redesigned from scratch.
The only way is to recreate your rules manually, but if you have a list of IP or MAC addresses you want to reuse, you can use
Rules - Add Batch in the main menu to add more than one rule in one go.
In addition, versions 3.x support so-called streams, which allow you to have more than one IP or MAC address under a single rule where each gets its own quota and bandwidth limit. In many cases this means you have a more compact ruleset - so please check the
user manual for new features.