Actually, I am not sure there is a trainer for those skills in Darnassus (Night Elf Main City). If that is the case you will have to go to Auberdine. To get there you must enter the big red teleporter behind the bank in Darnassus, which will teleport you to a dock beneath Teldrassil (The huge tree Darnassus lie in). From there you can either take a boat, or take a gryphon to Auberdine.
If memory serves, there should be either a Blacksmith or Mining trainer there. Not entirely sure. If not, you must get to Ironforge I guess. To do that, you must take a boat from Auberdine (the boat opposite the one to Darnassus, just take the left pier when you leave Auberdine) and get to Menethil Harbor. From there you just have to follow the road through a land of pain and death (for someone your level) called Wetlands. After a while you will get to run between orcs and more orcs, and finally, after running like hell for God only knows how long, you will get to Dun Morogh. Follow the road still, and after a while you will find Ironforge. There I know for certain you can train Mining/Blacksmithing.
If you wish to avoid this trip from hell, just grind some silver and type:
/2 WTB Summon/Portal to IF
Hope this helps