Hello,
You initially set up Windows using your old email address, which is the administrator account on your device.
If you’ve made changes to your device, such as installing Windows updates, your PIN may stop working, and you may be asked to reset it. During the reset process, you’ll need to verify your identity using the administrator account. Or, if you only have the password sign-in option now and you forgot it, try resetting it from the Windows sign-in screen by selecting the 'I forgot my password' option, as shown in the screenshot here.
alternatively,
Since you forgot the password for the old Microsoft account, have you tried resetting it using another device?
If this is a personal account, please use the following link to reset the password:
https://account.live.com/ResetPassword.aspx
Use your updated password to sign in to your device. Make sure it’s connected to the internet so the new password can sync.