Pour l'instant rien je pense : https://help.minecraft.net/hc/en-us/...-Migration-FAQ
Can I migrate my legacy Minecraft account to a Microsoft account?
Not right now. We'll have a solution for this soon, but for now, you can keep using your legacy Minecraft account to log in.
What is a legacy Minecraft account and how do I know if I have one?
Legacy Minecraft accounts were used from 2010 to 2012. You know you have one if you log in with a username instead of an email address.