Xiaomi's mobile phone calculator can't directly calculate the root number of the cube. However, this operation can be achieved by the following steps:

1. Open the Xiaomi mobile phone calculator application.

2. Enter the value that needs to open the root sign to the third power.

3. Press the equal sign (=) button, and the calculation result will be displayed on the screen.

4. Use other available calculation tools or manual calculation to obtain the result of root cube.

Please note that Xiaomi's mobile phone calculator has limited application functions and may not be able to perform some advanced mathematical operations. If more complicated mathematical operations are needed, it is recommended to use professional mathematical software or online calculator.