Apple iPad Pro 12.9 (2021)
iPadOS 15.0
1. Find "Mobile Data"
Press Settings.
Press Mobile Data.
2. Turn automatic use of mobile data on or off
Press the indicator next to "Wi-Fi Assist" to turn the function on or off.
3. Return to the home screen
Slide your finger upwards starting from the bottom of the screen to return to the home screen.