All you need to do is a search here for a type of ore and you should get a map of different zones that have that ore .
Example here http://wow.allakhazam.com/db/object.html?wobject=22
At Roughly level 10 is copper , level 20 is tin , level 30 is iron , level 40 is mithril and so on to the end game ores , as you go through zones as you level you will find various different ore nodes so it is hard to give exact levels of each type of ore node and these days with so many farmers on my server at times it can be hard to find any ore
What you will find is the rarer ore like silver and gold for example can spawn anywhere and usually the same spot that other ore nodes spawn, best tip i can give for mining is search around all mountains and look in all the caves as they usually have a few nodes of ore but of course usually have mobs to fight your way through to get to the ore , but exp for the killing is a good bonus on top of the ore and of course whatever else drops off the mobs is also a bonus.