A new Muslim is not to make up    missed Islamic duties before accepting Islam
Question

                A man accepts Islam and he is 40 years old. Does he need to make up what he has missed from his prayers?
Praise be to Allah.One who accepts Islam is not to make what he or she has missed from prayers, fasting, alms (zakaat) during his or her days of disbelief (kufr), as indicated by the verse in which Allaah says (what can be interpreted as):
Say to those who have disbelieved that if they cease, what has previously occurred will be forgiven for them… (Al-Anfaal:38)
And what was related that the Prophet (may the peace and blessings and mercy of Allaah be upon him) said, “Islam annuls what came before it.” (narrated by Muslim in his Sahih, no. 121). Also, the Prophet (may the peace and blessings and mercy of Allaah be upon him) did not command anyone among those who accepted Islam to make up for anything that he previously missed from the rites and rituals of Islam during his days of disbelief, and the scholars of Islam are in consensus about this.