Muslim female is not allowed to marry non Muslim man under any circumstance. Your marriage with non Muslim man was valid when you were non Muslim. The time you became a Muslim, you must give him the option to become a Muslim, then he can continue with you as a husband. f he refuses to become a Muslim, the marriage bond between you (Muslim) and him (Non Muslim) is finished.
You need then to keep Iddah of Wafaat (four months and ten days), then you are free.
I advise you to respect the law of the land as well and do not do anything which is against the law of your country.