On this page of the Mr. Prepper guide, you will find information on how to get a pickaxe.
Pickaxe in Mr. Prepper is necessary for exploring the mine and obtaining materials, as well as unlocking further corridors. It can also be used as a very durable weapon. You can buy a pickaxe from Bob, the merchant from the mine - it will cost you $26. When a pickaxe's durability begins to drop, you should disassemble it at the workbench – this way you will get its blueprint.