This question already has an answer here:
I set an alarm for fajr and went to sleep. I woke up at the alarm time but was not in a clear state. I saw it was 6 pm and turned the alarn off. I can't remember if I firgot to pray but I have a feeling there was some sort of forgetfulness. Now I don't know what to do. How much prayers should I do to make up for this? How should I ask for forgiveness for this and how long for? Can I still pray the fajr or not?