Hi there Ran, my name is Gerardo, and I'm an Xbox player, just like you. I'll be happy to assist you with any questions or concerns you may have.
Please keep in mind that is not possible to sign in to Mojang with a Microsoft account, especially if you have not gone through the migration process. You can only sign in with Microsoft after migrating the account, which is not the case for you.
I assume you are trying to follow the procedure outlined in the following link:
https://help.minecraft.net/hc/articles/19615552270221
If you are unable to follow the procedure and cannot log in with your Mojang account to initiate the process, you will need to contact Mojang Support for assistance using the following link:
https://help.minecraft.net/hc/requests/new
Note: This is a non-Microsoft website. The page appears to be providing accurate, safe information. Watch out for ads on the site that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the site before you decide to download and install it.
It is important to select "Migration Support" as the question category and specify in the details section that you cannot begin the migration process because you cannot log in with your Mojang account on the Minecraft website. They manage those accounts before the migration, and only they will be able to assist you.
Thanks for your understanding and I wish you good luck.
Best regards.
