I need to know where to mineFollow

The best zone I've found for mithril is Tanaris. You might be a smidge low for that zone though. But you could give it a shot. Run around the outside of the zone along the foothills. You can easily get about 20 or so mithril ore in a circuit. You'll have to do some mob dodging for a while till you get closer to 45ish. Especially in the southern part of the zone.

Otherwise, I've mined some mithril in the southern part of STV, and a little in the Badlands. As far as truesilver, that's a rare spawn like gold and silver, you'll find it occasionally but it's pretty infrequent. I don't know of any real places to go exclusively for it. Check out the guides section, there's a decent mining guide with a break down of zones for ore, etc.

Alterac mountains is the best choice to your lvl, you can find mithril and iron, in a circuit you can get 10/20 of each one.