Hello! Your iPad has gotten into Recovery Mode.
To get out of recovery mode, make sure your USB cable is connected to both the computer running iTunes and your device.You may need to hold the home button while connecting your USB cable.
Now hold the home and sleep/wake buttons together until you see the Apple logo appear. Don’t let go until then – it can take several seconds: the recovery graphic will disappear and a black screen might be shown for a while, but keep holding the buttons down until the white Apple appears.
Leave the USB cable connected until your device boots up and shows the lock screen. It’s now out of recovery mode.