Exchange Minecraft Microsoft for Mojang Account?

Today I bought a new Minecraft account for my Youtube channel. I bought this on the Mojang site and was then able to log into the Minecraft Launcher with the Microsoft account. However, I have 2 other accounts that I have saved as Mojang and not as Microsoft accounts. Can one of you perhaps tell me whether and how I can add the Micorsoft account to my other two accounts, i.e. Can make the Microsofr account a Mojang account?

Not at all, you have to wait until your Mojang account is migrated to Microsoft. Everything is described on the Mojang page / Support / FAQ.

Thanks