Recently I renewed my passport but my old passport in which visa for usa was stamped ,got lost. What am I supposed to do?

You are supposed to report a lost or stolen passport immediately to the proper authorities.

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Contact your countries passport office FIRST... if you haven't already. They will know what to do and how.

I would contact the US Embassy as well about the VISA so they can flag it so someone impersonating you won't use it.

You must report lost or stolen to the nearest US consulate and then apply for a new visa.