If you go to Joomla and search through the plugins there are tags, red and green, that show which ones are compatible with the old and new Joomla versions. They say 1.0 native or 1.5 legacy. That's the only thing I have been able to figure out. I'm brand new to Joomla and it's taking me awhile to figure things out too so don't feel too bad.
Marie Alline