Core Keeper

To go from level 0 to level 100 you need 59978xp.
You gain mining xp by hiting a wall and not destroying it, so a wall that take 10 hit will give 10 xp, but a wall that take 1 hit will give 1 xp. BUT it's when you destroy the wall that the xp is granted.

Note : Hitting indestructible wall or punching a wall when you dont have enouth mining power will not grant xp you need to destroy the wall for the xp to actually count.

To power level it and do it in about 4hours you need an "hand drill" and not the drill that you use for giant ore.

The first drill that you can find is drop from ghorm the destroyer that you can respawn to farm is handrill. the hand drill have 85 mining power at level 1 but can go to 1063 at level 19 so you can only need one if you want or have the ressource or, you can go fishing in the azeroth wilderness for a 1/50 to obtaine the scarlet handdrill starting at 327 at level 1 and can go up to 1198 at level 19.

When you got a drill go into the far corner of the map where there is a lot of blue crystal wall and start digging in straight line. Every wall should take about 4-6 hit to break and give around 5xp. After your first 9999block you should be level 100. The drill can tap 5 time per second so it's about 2hours of mining none stop. if you dont count the moving betwin block and repairing that why ot should take a good 4hours.

To go even faster you can farm an obliteration ray and evolve it into the stormbringer but it's even more time consuming than just farming whit the scarlette because your basse mining damage will be 800 and 1000. In that case the best place to farm is the last biome of the word to the limit of the world. Whit the stormbringezr it should take also 5 hit to destroy the wall.

Good luck.