Where can I find the value of cards from the Dragon Ball Z Trading Card Game?
You have a few options actually.


TCGPlayer: Will give you market price and median 
Ebay  : Will give you what people are asking for the cards
AlternativeWorld: Seems a bit outdated, but it may help. 


Hope this helps. 

Edit: Also I noted that in your question you referred to it as CCG (Collectible Card Game). If you do your searches with TCG (Trading Card Game) it probably turns out more results.