Steam Guard Backup codes

If you don&know how to change your Steam Guard Number you can do it by following these instructions. (Unfortunately, you must have your account logged somewhere, in your Pc, browser, or in some other device) 1. Go to your Steam account, click on your photo and go to Account Details. 2. Scroll down to "Contact info" and choose "Manage your Phone Number", then click in Change Number. 3. You can pick 3 options to change your number, you can choose by your preference.