How many mines are there on Earth, and what is their output in tonnes?
You can get estimates from the USGS mineral yearbooks. For example, the entry on Australia has a data table with the amounts of mined resources. Or, the entry on copper lists both US production and international production, including numbers of people employed.

More number are available from government statistics websites, regarding employment. For example Australia and USA.

Digging through those websites will give you an order of magnitude of what to expect.