Thank you for letting me know.
Since the Mojang to Microsoft account migration deadline passed on September 19, 2023, any Mojang account that wasn't migrated in time can no longer sign in to Minecraft.net or the Minecraft Launcher.
At this point, the best step would be to contact Minecraft Support directly here: https://help.minecraft.net/hc/request/new
Just a heads-up: it’s unclear if this is still available post-December 2023. Provide as much detail as possible, including your original Mojang account email, username, and purchase details.
I know it’s disappointing, especially when you just want to play again after a long time. If there's anything else I can help clarify, I'm here for you.