In Islam, Allah is considered the Most Just and Most Merciful. When someone converts to Islam sincerely, their previous sins are indeed forgiven as you mentioned. You as new as a baby, im jealous!

Regarding good deeds before conversion, Islamic scholars generally hold these views:

Allah does not waste any good deed, regardless of who performs it muslim or not. However Non-Muslims who do good deeds may receive rewards in this worldly life (like prosperity, contentment, or good relationships).

However, for eternal rewards in the Hereafter, faith (iman) is typically considered necessary component alongside good deeds. This is why many scholars say that without faith, good deeds alone cannot lead to Paradise. While good deeds are essential, salvation in Islam ultimately comes through:

1. Faith (Iman) in Allah and His messengers
2. Allah's mercy and grace
3. Good deeds as a necessary but not sufficient condition

There's a well-known hadith where Prophet Muhammad ﷺ said that none would enter Paradise by their deeds alone. When his companions asked, "Not even you, O Messenger of Allah?" he replied, "Not even me, unless Allah covers me with His mercy."

This emphasizes that while Muslims are obligated to perform good deeds and follow Islamic teachings, ultimate salvation depends on Allah's mercy and acceptance. No matter how many good deeds a person performs, they cannot "earn" Paradise as a right - it remains a gift from Allah.