For Mining I have no idea where the pickaxe is can somebody help me?

The Pick you used to start with was probably just for encouraging testing of mining, and now that its been tested some, its more reserved to progress.

You can make your own Pickaxe with 3 ingots, get them hot and put them on the anvil, then radial select "Large Axes"

Hit it till a double axe head is forged, and then hit it again to turn it into a pickaxe head

• Then you can take it and combine it with a 
  • 2h handle - "you created a (metal) pickaxe!" <--- notification that tells you, you've successful made a sellable item - Any item that gets a notification like this, can be sold to a customer, regardless of how you constructed it.  If you don't receive this message, it cannot be sold to an npc
  • 1h handle or Pole grip - As far I know Your character, the Blacksmith, Can still equip /any/ pickaxe - whether its 1h, 2h, or pole grip; They won't say You've created a pickaxe, but you'll still be able to equip it (press e while looking at it, if you already have one equipped, make sure you select it before trying to equip, or you'll just grab thin air in its direction.)
    • 1h 2h and pole grips apply for Hatchet and mallet too, Afaik. Though i haven't tried in 0.0.82, nor pole grip with small axe head - I did most of my testing in 0.0.81 - You can always try things out free of worry in sandbox mode though. check it out there before committing to a crazy looking personal weapon.

Edit - Man Itch.io's post boxes... sure leave a lot to be desired :l