What is my duty and what is the amount of expiation in Saudi Riyals for the Ramadan days that I missed and do not remember whether I made them up or not?

If you are certain that you broke your fast on certain days of Ramadan and doubt whether you have made them up, the original ruling is that they remain an obligation upon you. You must investigate and make up what will absolve your responsibility before Allah. The best approach is to be cautious and make up the greater number if you are undecided between two numbers. As for the expiation for delaying making up the fast until another Ramadan, it is a mudd of food. The original ruling is to give out food, not its monetary value.