where do I get a security key?

You can buy them from Amazon, etc.

Here's the Apple article about security keys:

About Security Keys for Apple ID - Apple Support

What's required for Security Keys for Apple ID

• At least two FIDO® Certified* security keys that work with the Apple devices that you use on a regular basis.
• iOS 16.3, iPadOS 16.3, or macOS Ventura 13.2, or later on all of the devices where you're signed in with your Apple ID.
• Two-factor authentication set up for your Apple ID.
• A modern web browser. If you can't use your security key to sign in on the web, update your browser to the latest version or try another browser.
• To sign in to Apple Watch, Apple TV, or HomePod after you set up security keys, you need an iPhone or iPad with a software version that supports security keys.

heathherthesaint1 Said:

"where do I get a security key?: I am looking for a security key for your passwords and I don't know where to find it or exactly how they use it but my accounts are being hacked and all my info is all in the dark web. please help"

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Find the Security Key in the original packaging.

Troubleshooting Compromised Accounts:

I. Use Find My: Use the Find My App to Locate a Missing Device or Item - Apple Support

If Find My was enabled with this, then you may be able to locate it there. Note that this is based off of the last time the device they were connected to was itself connected to the internet.

II. Secure your Info:

If concerned for device access, then (A)verify your devices, and (B)secure your account:

A. Verify your Devices:

Verify that all devices are logged in to your account, by using this link: Check your Apple ID Device List to See where you're Signed in - Apple Support

then...

B. Modify your Credentials:

Having been stollen, someone lily has your credentials. So, by all means, modifying them.

• Modify: your login credentials (Using Both a New eMail and a New Password for each and all sites)
• Associate: a different method of payment to your account
• Enable: Two-Factor Authentication for Apple ID and for all other accounts that have such an applicable option