Answered by Ustadha Naielah Ackbarali
Question: Is it necessary to make up missed prayers of all the years for a new convert?
Answer: Upon converting to Islam, all previous sins are forgiven, alhamduLlilah. Additionally, one does not have to makeup any prayers or fasts missed for the duration that one was non-Muslim. The Sacred Law rulings related to worship only apply to Muslims.
After one converted to Islam, if one subsequently missed any obligatory fasts or obligatory prayers, then one is obliged to make them up.
Please see this related link:
Checked & Approved by Faraz Rabbani
Ustadha Naielah Ackbarali is a female student of Islamic knowledge from the US. She studies with leading Hanafi scholars from Syria and elsewhere.