My account had been hacked.

It is a scam.

Did you provide any potentially damaging information to anyone? If yes, you'll need to follow up, for example, with a credit card company, Apple, your bank, etc.

If you gave you Apple ID password to a scammer, then

Change your Apple ID password https://support.apple.com/en-us/HT201355

Here is What to do after you change your Apple ID or password https://support.apple.com/en-us/HT204071

Learn about Phishing, Scams, Apple Practices,etc.

 See If you see apple.com/bill, itunes.com/bill, or an unfamiliar charge on your statement https://support.apple.com/en-us/HT201382

See Identify legitimate emails from the App Store or iTunes Store https://support.apple.com/en-us/HT201679

See How to avoid scams when using Apple Pay to send and receive money https://support.apple.com/en-us/HT208226

For scam related information from Apple including reporting scams to Apple see Avoid phishing emails, fake 'virus' alerts, phony support calls, and other scams https://support.apple.com/en-us/HT204759

Identify scams related to purported apple notificationsper Eric Root.

“Apple will always address you by your name or the name they have on file for you, not Dear Customer, Dear Client or by using your e-mail address. The e-mail will be from @apple.com or @iTunes.com. E-mail addresses can be spoofed. You can go to Mail/View/Message/Show all Headers to see more. Apple emails won't have poor grammar/misspellings. Apple e-mails will never contain an attachment. Apple will never request personal information by email such as Social Security numbers, your Mother’s maiden name or full credit card numbers. …

“The only exception to the above I have noticed is if you order something from the Apple Store (apple.com), your receipt will be addressed to Dear Apple Customer. That is a receipt for a purchase you initiated.”

Learn about/Increase security

See If you think your Apple ID has been compromised https://support.apple.com/en-us/HT204145

Increase the Security of your Apple ID https://support.apple.com/en-us/HT201303

iCloud security overview  https://support.apple.com/en-us/HT202303

Ways to keep your information safe on Mac https://support.apple.com/en-gb/guide/mac-help/mh11402/mac

That indicates that they would like to hack your account (via phishing), not that it is hacked. If they had already hacked your account they wouldn't be trying to get your password that way. Anyone can send an email to anyone without hacking. If you want to report the email to Apple see: Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support

Your account hasn't been hacked. You received a bogus email.

• Apple does not include document, or PDF files to download.
• Apple would not refer to you as Dear Customer, Dear Client, or anything other than the name on file for your account.
• Apple would not have such horrible spelling or grammar. 
• Apple would not send a message to “Undisclosed Recipients”. 

It is a phishing attempt. Do not respond. Do not divulge any personal or financial information. You can use the address below to forward the suspect email message, as an attachment to Apple.

reportphishing@apple.com

If you provided your Apple ID and password at the bogus site, change your password immediately.

  https://support.apple.com/en-us/HT201355

The links below have information to help identify fraudulent emails.

Identifying legitimate emails from the iTunes Store

https://support.apple.com/en-us/HT204759