Activation Lock is requesting password from lost iPad

You have likely received a phishing (scam) email from whoever is in possession of your stolen device - and with this email, the perpetrator is attempting to fool you into revealing information that will allow your iPad to be unlocked and reused.

See >>> Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support

If you are unsure of the source or provenance of a message or alert, do not respond to, or engage with, the message. Certainly do not, under any circumstances, attempt to contact anyone using the contact details or links that have been provided within the message itself.

If you need to verify a message from Apple, make independent contact with Apple Support - using the Support link that you will find at top-right or bottom left of this Support Community page - or other legitimate Apple website. I could provide the link here - but that would undermine you finding and using a legitimate trusted link to Apple Support.

Most scam alerts are designed to scare the unwary into giving away sensitive information - or to fool you into doing something that you shouldn’t - usually to defraud you financially, or in this case to gain access to a stolen device and/or your AppleID account.

If you suspect that your AppleID has been compromised, follow the advice outlined here:

If you think your Apple ID has been compromised - Apple Support