Yes, first, I would say, if I were in this situation, I would pray for him that the Lord grant him the grace of faith. Faith is a gift of God; it is not about my conviction. I would also give him good, Catholic explanations of the faith. Probably, it could even help to provide examples of converts from Islam who explain why they abandoned Islam and found Christ as their Lord. It could also be as simple as telling this person to be honest and not fear the truth.
You can investigate the Catholic faith and share examples of conversion. But this should be accompanied by prayers for the person who is seeking Christ or is interested in Him. I have frequent conversations with Muslims, but usually they are not deeply Islamicized. The majority do not know the Quran or Sharia fully; they follow the tradition of their family. They say, "My family was Muslim, my parents, my grandparents, I was born this way," and they continue the tradition. They pray, go to the mosque, and nothing more. Their knowledge of Islam is often superficial, so they remain Muslims mainly because of tradition.
A minority studies Islam deeply in schools and becomes convinced that it is the will of God and that the world must be Islamicized. Yes, this exists, but most are not like that. We must speak with Muslims and invite them to pray. My experience is that some people from Muslim backgrounds come to church simply seeking silence and an experience of quiet to pray and to find God.
They find this in the Catholic Church. For example, we have Perpetual Adoration of the Blessed Sacrament, and the church is open all day. Some people come simply to spend time in silence. Here, the Lord begins to work in them. They notice a difference compared to the mosque. Some later convert because of this experience of deep peace in the Catholic Church. They feel a presence of God there, even if they do not fully understand it. This, I think, is the first step on the path to faith.