The message that you see would suggest that your iPad is centrally managed by a Educational or Enterprise establishment - and has management profile installed.
Devices that are configuration locked by an MDM platform can usually only be released from central management by the platform that manages the device. Be aware that Apple will not assist with removal of management profiles.
Unless you are lucky - and have the option to delete the profile from iPad Settings - you’ll need to seek assistance directly from the System Administrator who manages the device.Â
Install or remove configuration profiles on iPad - Apple Support