I am of 25 years, 3 years of marriage, planning for pregnancy but I heard that if there is pain during period then it will be problematic in pregnancy so can you tell me any treatment or medicine or exercise, so thet I will not suffer from pain during period

That is a wives tale. Don't pay it any mind. Nothing you can do will severely alter your period and how painful it is. Nor is that a sign of how bad the pregnancy will be. My wife had glorious periods like you see in commercials with bunnys, dancing in white pants, and all that fun stuff. She had a very problematic pregnancy. That is anecdotal I know.