All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
You have to know that your marriage to that woman was nothing but fornication as it did not meet the conditions of a correct marriage. However, you did well by repenting. Even if we suppose that your marriage to that woman was correct and fulfilled the conditions of a correct marriage, you do not have to inform this woman whom you want to marry that you were already married before. So why would you tell her since it was not a correct marriage? It is an obligation for whoever has committed adultery or fornication to conceal his sin and not inform anyone about it. The Prophet said: "Avoid this filthy thing [fornication and/or adultery] that Allaah has forbidden, and whoever has committed it has to conceal himself." [Al-Bayhaqi]
Even if we suppose that the woman you propose to for marriage or any other person asks you about it, you can use Tawriyah (saying something which has more than one meaning and intending a meaning different from what the listener is likely to understand). For instance, you can tell her that you were not married before, intending to mean that you were not married in correct marriage before, and you can tell her I did not commit fornication, meaning that you did not commit fornication after having repented. So a Muslim uses this method of Tawriyah when needed.
Finally, it should be noted that in order to be grateful and thankful to your Lord for the blessing or repentance, you should avoid any means that could lead you to committing fornication or adultery again.
Allaah knows best.