Attach this word onto the end of a prefecture place name and you have the prefecture portion of _____ prefecture. These are a lot like states or provinces.
The reading for this is the same as what you learned with the kanji, probably because it's always attached to things (so it's like jukugo). Don't write the 〜 when you're writing in the answer, just the けん portion, and you'll get this one correct.
What prefecture are you from?
I have been to Ishikawa prefecture three times.
Yamaguchi prefecture's specialty is puffer fish.