My iPad is locked from one of my previous employees who is not cooperating.

Here are the Apple support pages that outline the Activation Lock - and the only mechanisms by which it can be turned off:

https://support.apple.com/en-us/HT201365

https://support.apple.com/en-gb/HT201441

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/keeper, 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 may assist assist - otherwise Apple will decline to help and nobody here will be able to offer alternative solutions.

If you are the owner of the AppleID that previously activated the device - and you have forgotten your AppleID or associated password, these can be recovered here:

https://iforgot.apple.com

To recover your credentials, you’ll need access to one of the following:

• Your primary email address mailbox that corresponds with your AppleID
• Any of the secondary/recovery email addresses that should be configured for your AppleID account
• Any of the trusted telephone numbers (fixed line or Cellular/Mobile) that are associated with your AppleID

Unless you AppleID account has not been fully/correctly configured, or has been seriously neglected, recovery of the AppleID and password should not be difficult.

More information about recovery of your AppleID:

https://support.apple.com/en-us/HT201354

More information about recovery of your AppleID password:

https://support.apple.com/en-us/HT201487

When you recover access to your credentials, you would be well advised to log-in to your AppleID account from a web browser - and verify/update any email addresses and trusted telephone numbers:

https://appleid.apple.com

I hope this information and guidance proves to be helpful in resolving the issue.

If it's only a matter of passcode to unlock the screen, these are the instructions to reset it:--> If you forgot the passcode on your iPad, or your iPad is disabled

It it's a matter of Apple ID, things are more complicated. If you still have the proof of purchase (receipt or invoice) of that device, you can contact an Apple Store, show them that document, and they will unlock that activation lock.

Without that document, only the previous owner, using the credentials that were used to activate that device, can unlock it. Without those credentials, that device is useless to you.

If your employee doesn't cooperate, and you can demonstrate you are the original owner, I'd contact your lawyer.

Regards

Giulio