How to turn on stolen device protection of my ipad that is stolen

Stolen Device Protection is not available on the iPad. Even if it was, it would need to be done before the device is stolen. Are you able to use Find My to track and erase the iPad?

Never give your Passcode or Password to anyone. Nothing good comes from doing that.

Reset your Apple ID password: If you think your Apple ID has been compromised - Apple Support

Enable two-factor authentication on the Apple ID, if that is not already enabled.

Verify your trusted telephone numbers and email are as expected, and run Safety Check.

Details on that: Personal Safety User Guide - Apple Support

Enable lost mode: If your iPhone or iPad is lost or stolen - Apple Support

If you had Find My turned on, then Activation Lock is on as well. You can use these link to erase and find your iPad:

Erase a device in Find Devices on iCloud.com - Apple Support

https://www.icloud.com/find

As long as she does not know your Apple ID Password, she will not be able to remove Activation Lock. Just make sure you do not remove the device from Find My. If it was not on previously, you will not be able to turn it on remotely.

Don't concern yourself with the scams claiming they can remove the Activation Lock. They are only there for the clicks and to get you to purchase software that does not work. Many people have fallen for this trick even though they show paid reviews claiming that it works.

My concern with the Apple ID password: it is possible to take over an Apple ID given a trusted device and a passcode.

It’ll be an account takeover; really obvious.

I’m also unwilling to assume somebody that has the passcode and swiped an iPad didn’t also get the password.

The faster that iPad gets untrusted and locked, the better.