Help me to change key recovery

You need to enter in the phone number it is asking for. Check with family, friends, carriers, emails, etc.

Otherwise if you have access to another Trusted device you can try to update your Trusted Number following “manage your trusted phone number” at  https://support.apple.com/en-us/HT204915#trusted 

The link shortcut shoeluver13 provides no longer works. What you are looking for is the section near the end of the document:

What is a trusted phone number?

To use two-factor authentication, you need at least one trusted phone number on file where you can receive verification codes. If you have a phone number that isn't associated with your trusted device, consider verifying it as an additional trusted phone number. If your iPhone is your only trusted device and it's missing or damaged, you won't be able to receive verification codes required to access your account.

To see, add, or change your trusted phone numbers:

• On your iPhone, iPad, or iPod touch: Go to Settings > your name
• > Password & Security. Next to Trusted Phone Number, tap Edit.
• Choose Apple menu  > System Settings (or System Preferences),
• then click your name (or Apple ID). Click Password & Security, then
• add or remove a trusted phone number.
• Go to the Account Security section of appleid.apple.com.