Are you using emulator or the game console? What I know is they called game card in the game console and the problem of M1 backup thing is found in my emulator so I can't decide which one are you using. But, if it's for emulator, I can help. I've just read it in one of other posts,though. But, I've tried it myself too. It works.
You need to use VBA for this advice. In VBA menu bar, choose Options/Emulator/Save Type/Flash 128K. The upper one is just automatic.
Clear all your corresponding save files for that game. Leave only that rom file there and restart the game again. When I did that, that message of M1 backup thing isn't coming out again and can save and load the game.
I'm sorry if you are using game console and sorry if I misunderstand it with game console.