How can get my recovery key

If you have forgotten it, there isn't a way to get your Recovery Key. From the article below.

Using a recovery key is more secure, but it means that you’re responsible for maintaining access to your trusted devices and your recovery key. If you lose both of these items, you could be locked out of your account permanently. With that in mind, it's important to keep your recovery key in a safe place. You might want to give a copy of your recovery key to a family member, or keep copies in more than one place. That way you always have your recovery key when you need it.

How to generate a recovery key - Apple Support

You can try to make a new Recovery Key using the steps in the article above.