Charge the battery
Your Magic Keyboard with Numeric Keypad, Magic Mouse 2, and Magic Trackpad 2 each have a built-in rechargeable battery.
Charge the battery. Connect your Magic Keyboard with Numeric Keypad or Magic Mouse 2 (or optional Magic Trackpad 2) to your Mac Pro with the included USB-C to Lightning Cable. To check the charge level, click in the menu bar at the top of the screen, then choose the device. If you don’t see the Bluetooth icon in the menu bar, in System Preferences, click Bluetooth, then select “Show Bluetooth in menu bar.”