mithril oreFollow

It would be easier if we knew your level...

However, mithril ore can be tough to find in large quantities, but is easy to find spread out across a zone. Places like the Hinterlands, Tanaris, the Badlands, and parts of Felwood/Azshara/Searing Gorge have a decent amount. In Felwood and Azshara, you'll find thorium in the tougher parts; in Searing Gorge you'll find Dark Iron. Tanaris will have some iron in it, as will the northern part of the Badlands.

I feel like the Badlands might have the most. Try running a sweep of the souther mountain range. Whenever you see earth elementals, run into that part of the mountains as well.

Also, look for caves in areas. Caves usually hold some ore; you can find mithril in Thousand Needles and Feralas in the caves (Silithid caves in particular are good for them).

It is tough to find mithril in large quantities, however.

whenever I want to find out where to mine, I use this site's search feature. Typing "Mithril Deposit" into the search box yields this result. Clicking on "Mithril Deposit" there gets you to this screen. Then you can go and look at individual maps. This can be done with any ore you are interested in finding.