Eminent Shaykh, I did not fast for three days in Ramadan without a valid excuse when I was fifteen and seventeen. But now, my Lord has bestowed upon me the favor of guidance, Alhamdulillaah. Now I am twenty-one years old. How should I make up for those fasts? Is fasting only due upon me or fasting as well as an expiation? I am now making up for the second day. Is it necessary to make any expiation before fasting? In case it is true, what about the two days I have fasted, since I intended to make up for three fasts?
All perfect praise be to Allah, the Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His Slave and Messenger.
Whoever fulfills the requirements of the obligation of fasting, i.e., being of age (i.e. having attained puberty), being sane, conscious and healthy, and yet intentionally breaks fasting on a Ramadan day, two things become due on him/her: first, to repent from that sin and second, to make up for the broken or missed fasts. If these fasts were not made up for until the next Ramadan had come, it becomes incumbent, in addition to making up for the fast, that an indigent person must be given food, for each day on which fast was not observed. However; in case of ignorance of the prohibition of delaying makeup fast until the next Ramadan comes, no expiation will be due.
It is preferable to offer food in coincidence with makeup fasting, i.e. to fast a day and then offer the expiatory amount of food for one day, and so on. Nevertheless, offering expiatory food can be done before or after observing a makeup fast.
Hence, the questioner can give expiatory food after observing makeup fast for those days.
Allah Knows best.