The Sharī‘ah is silent on the
issue of missed prayers in one’s previous life. Scholars have formed different
opinions on this issue. One group says that one must count each and every prayer
missed out and then start offering it until they are completed. This is the view
of some Hanafite jurists. Imam Ibn Taymiyyah is of the view that one should make
a rough estimate of the missed out prayers and start praying them in place of
praying sunnah or nafal rak‘āt. Imam Ibn Hazm holds the view that one does not
need to offer the missed out prayers at all. Mere repentance is enough.
You can choose the opinion which appeals
most to your intellect.