Hacking

It's extremely unlikely it's hacked to begin with, but restoring to factory condition would normally eliminate anything on it including any potentially unwanted software.

There is no known method to remotely hack iPhones or iPads currently. Unless you let someone your iPad for an extended period of time near a computer whatever may be happening is probably not a hack.

If you explain what is happening then someone may be able to help you resolve it.

What leads you to believe that your iPad may have been “hacked”?

Due to the system architecture of iOS/iPadOS, unless jailbroken, your iPad is not susceptible to traditional malware infection per-se. However, as with all computer systems, there are still vulnerabilities and exploits to which you remain vulnerable.  For older devices, no longer benefiting from regular security updates, the risk of an unpatched vulnerability being exploited increases.

Be wary of the often repeated myth that Apple devices are immune to malware. Consider that if the myth (and over-generalisation) were true, Apple would not expend considerable resources, as they do, in developing and issuing regular software security updates.

Assuming that your iPad has not been jailbroken, restoring your iPad to Factory Settings will completely erase the iPad and eliminate any lingering malware. The factory restore will install a fresh copy of the most recent version of iOS/iPadOS supported by your iPad.