Do I need to sleep with someone to punish my husband for his affairs?

I am a Christian girl with two children, going to convert to Islam. I am getting divorced due to my husband's affair. My husband has had a lot of affairs before and after marriage with me. Now I am going to marry my old friend; he is a Pathan . He told me that after talaq with my husband, I have to sleep with someone as a tradition. This is a punishment for my existing husband. I asked him how it will be a punishment for him; it's a punishment for me. I don't want to sleep with anyone. My friend says that, in Islam, it is the tradition in Karachi , Pathan.