I have Audiator 3, which came with "Ages Soundpack" "Defult" and "Halo". How do I get those sounds from there to my list of sounds in conversations?

Audiator three and the new Custom Sounds feature of Plus! are unrelated.

Although I think it is possible to import the sounds from the Audiator packs into Plus!

Well I got the Stuffplugin NG, but uninstalled it because I didn't see the point of having it and it left behind Audiator with those sound packs.
The picture show the list of sounds. I want to be able to use all those sounds in conversations, just like the built in sounds...

Then you need to import all those sound in the custom sound library (one by one), just as you would add any other new and home made custom emoticon sound...

Or you could browse some sites for custom emoticon soundpacks based upon the Audiator's soundpacks. Some are already converted and ready to be used:
* http://www.mpsounds.net/
* http://shoutbox.menthix.net/showthread.php?tid=41508

Okay. I thought there might be a way to import them all at one time, but there isn't. So what is the point in Audiator 3?

Audiator was origianly released before the Custom Sounds feature of Messenger Plus!