How can I create an MP3 alarm clock?

I would like to create an alarm that activates an mp3 file to wake me up in the morning, does anyone know how to do it?
I would like to be able to make sure that with a case attached to the Raspberry Pi start the mp3 file

You can achieve this with a media-player component. Which one is up to you. If you want to play from the same Pi that you run HA on you could just use VLC with the VLC-component.

Create an automation that uses the time platform, like this: Simple time based Automation

I have S.O. HASS.IO installed

Maybe you can use the Mopidy addon:

Your media-player platform would then be MPD

how can I proceed?

Look at the link I gave you about time based automation. What you need to do is create an automation that triggers on the time-component. And reacts by playing an MP3-file to the MPD server (or start a wake-up playlist instead).

I don’t have my HASS-install here right now so I can’t give you any code, I’m sorry.

I can wait