As described, the iPad is Activation Locked to the AppleID of the employee.
As you are clearly not centrally managing your corporate devices using an MDM Platform - as might be considered both normal and good practice in a Business or Educational environment - you’ll need the AppleID credentials that were last used to activate the iPad.
Here are the Apple support pages that outline the Activation Lock - and the only mechanisms by which it can be turned off:
Activation Lock for iPhone, iPad, and iPod touch - Apple Support
Turn off Activation Lock – Apple Support
As you will discover, unless you are the owner of the AppleID that was last used to activate the device, or unless you can secure the cooperation of the previous owner, you’ll not be able to defeat or bypass the Activation Lock. With documentary evidence that you are the original owner (such as sales receipt showing the serial number), Apple might assist - otherwise, they and nobody here will be able to help you.
If you have the necessary documentation, Apple have introduced a portal though which you may be able to request release of an Activation Lock:
How to remove Activation Lock - Apple Support & start an Activation Lock support request.