Asalamualaikum wrt wb,
All praise be to Allah.
Yes, the Prophet, peace be upon him, said, "Islam erases what came before it." You made a very wise decision to accept Islam, and inshallah whatever happened in the past has been erased for you.
However, it is not permissable for the man to marry you, since Allah says, "Pure and chaste men are for pure and chaste women, and pure and chaste women are for pure and chaste men."
Unless he makes complete Tawbah for his previous sin, which includes:
1.) Immediately stopping the sin.
2.) Regret and remorse for what happened, knowing that it was wrong, and feeling sad for having disobeyed Allah.
3.) Resolving to never return to the sin.
In this case, you may consider marriage, however, the requirements for the marriage include having a wali (since you are Muslim, you must find a Muslim wali from your family, if you have none, then the Imam of the community is your wali), having two witnesses, naming a mahr, however small or large, and an offer and acceptance by the groom and your wali.
May Allah make you firm in your relgion, and continue to guide you on the Straight Path.
And Allah knows best.