Status of a non-Muslim marriage if the wife accepts Islam?

If you reside in Russia or in any other non-Muslim country, the ruling with regards to you is that since the time you had accepted Islam, you will remain in the Nikah of your husband for three menstrual cycles (or three months if you are not menstruating). If he accepts Islam before the termination of three menstrual cycles, your marriage will remain intact. If he does not accept Islam within this period, your marriage terminates and thereafter, you will wait for another three menstrual cycles as Iddah. After this, it will be permissible for you to marry a Muslim man.

(Jawahirul Fiqh, Vol: 2, Pg: 134-135, Raddul Muhtar, Vol: 3, Pg 191)

And Allah Knows Best