Sorry to hear that you're having trouble unlocking your tablet. Can you please try pressing the Volume Down and Power buttons together for around 10 seconds to see if you're able to restart the tablet in this manner?
Alternatively, try heading to Find My Mobile via an internet browser, sign in with your Samsung account details and look for an option to remotely unlock the device from here. If you have set up "find my mobile" on your device, you should be able to remotely unlock it and change your pin to a new one.
