“use this iphone to unlock your Apple ID” pop up

That is not a message from Apple.

Looks like that someone is probably trying to hack your Apple ID, they probably have your email and password.

Click Don't allow.

To keep your Apple ID account secure, see the following Apple articles:

Manage and use your Apple ID

Manage and use your Apple ID – Apple Support (UK)

See who has access to your device or accounts

See who has access to your device or accounts – Apple Support (UK)

Recognize and avoid phishing messages, phony support calls, and other scams

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

• If you receive a suspicious email or SMS text message that looks like it's supposed to be from Apple, please email it to reportphishing@apple.com.

Phony "tech support" / "ransomware" popups and web pages

Phony "tech support" / "ransomware" popup… - Apple Community

Identify and filter junk mail in iCloud

Identify and filter junk mail in iCloud - Apple Support

If you think your Apple ID has been compromised

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

Identify legitimate emails from the App Store or iTunes Store 

Identify legitimate emails from the App Store or iTunes Store – Apple Support (UK)

Set up iCloud Keychain

Set up iCloud Keychain - Apple Support

Create a strong password for your Apple ID, It is best if your password consists of eight or more characters and include upper and lowercase letters, and at least one number. You can also add extra characters and punctuation marks to make your password even stronger. 

Never provide your password, passcode, security questions, verification codes, recovery key or any other account security details to anyone else. Apple will never ask you for this information.

See also the following Apple articles:

About the 'Trust This Computer' alert on your iPhone, iPad, or iPod touch

About the 'Trust This Computer' alert on your iPhone, iPad, or iPod touch - Apple Support

Authorize or deauthorize your computer for iTunes Store purchases

Authorize or deauthorize your computer for iTunes Store purchases - Apple Support 

Get a verification code and sign in with two-factor authentication

Get a verification code and sign in with two-factor authentication - Apple Support

Check your Apple ID device list to see where you're signed in

Check your Apple ID device list to see where you're signed in - Apple Support

• if you see devices that don't belong to you, delete from your account.

Block phone numbers, contacts, and emails on your iPhone, iPad, or iPod touch

Block phone numbers, contacts, and emails on your iPhone, iPad, or iPod touch - Apple Support

Detect and block spam phone calls

Detect and block spam phone calls - Apple Support 

Clear the history and cookies from Safari on your iPhone, iPad, or iPod touch

Clear the history and cookies from Safari on your iPhone, iPad, or iPod touch - Apple Support

Your Apple ID has been locked due to security reasons

See this Apple article: If your Apple ID is locked or disabled

If your Apple ID is locked or disabled - Apple Support (CA)

So at least it does seem that it must be coming from Apple 

Thank you for your feedback 👍

Thanks for your feedback & you're welcome.

One more thing, if you change your Apple ID password, see What to do after you change your Apple ID or password

What to do after you change your Apple ID or password - Apple Support