I've migrated but I'm still seeing my Mojang account or the Mojang login screen. For help locating your transaction ID, see What is a Transaction ID? Be sure to include your transaction ID from the purchase of your account. If you think your account has been migrated by someone other than yourself please contact Minecraft Support.
HOW DO I FIND MY MICROSOFT ACCOUNT HOW TO
For instructions on how to do this, see Changing Your Email Address (Mojang Accounts). You will need to change the email on your account first. If you do not have access to the email that is used to log in to your Mojang account, you will not be able to complete the migration. I don't have access to the email on my Mojang account If you forgot which email you used to create your Microsoft account for migration you will need to speak with Microsoft support to recover the email address used to sign-up.