I am a young Muslim man. I started praying when I was eighteen, Should I make up for the previously missed Salahs (prayers)? If yes,
how many years shall I make up for?
(Part No. 6; Page No. 44)
You should supplicate to Allah for His Forgiveness and repent to Him of what has passed. You do not have to make up for missed Salahs, because abandoning Salah is an act of Kufr (disbelief) as the Prophet (peace be upon him) said:
The covenant that distinguishes between us and them (the disbelievers) is Salah. Anyone who abandons it has committed Kufr.
There are many other Hadiths with this context. However, the expiation of Kufr is to repent to Allah (Exalted be He), and to do your utmost to offer righteous deeds as Allah (Exalted be He) says:
And verily, I am indeed forgiving to him who repents, believes (in My Oneness, and associates none in worship with Me) and does righteous good deeds, and then remains constant in doing them, (till his death).
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.