Hey,
The main command is /inmates.
You will need shiny diamonds in your inventory to purchase them.
The limit per cell is bugged, but you can place a maximum of 5 in your cell. Do not place 6 or you won’t be able to access or use them.
Once you place your inmate in a 5x5 area, it will start mining gems. Right-click it to open the menu to collect gems.
Currently, there is no fuel/food to speed it up, but you can still upgrade it within the menu.
Use the reforged gems to purchase masks at /reforger.