Do I have to undo my baptism to become Muslim?

Nothing to undo

Baptism is a Christian rite, usually performed on a baby who had no say in it. Islam doesn't have a counter-ceremony, because it doesn't see the baptism as something that bound you. The Prophet ﷺ said every child is born with a true faith in worshipping Allah alone, and his parents then bring him up as a Jew, a Christian or a Magian (Sahih al-Bukhari 1385). That is not blaming your parents. It simply says you were raised in the faith of your family, as most people are.

When you sincerely say the shahada, you enter Islam. That's all. For the basic rules about baptism and Islam, see Is there baptism in Islam?

What about church records?

You are not required to do anything with your church records. Some people like to write to their church and ask to be removed from the membership list, and some churches have a process for this. That is a personal and administrative choice, not part of becoming Muslim. You can do it, or leave it, as you prefer.

Godparents, family and traditions

This is often the harder part. If you are a godparent, you might not be able to take part in religious duties such as presenting a child for baptism or making Christian promises. You can still love your godchild, stay in touch and be a good influence. See Can my child have godparents as a Muslim? for how Muslims think about the role.

The Quran teaches kindness to parents even when they follow a different path:

So you can sit with your family at the table, visit them and care for them. What you avoid are acts of worship that go against Islam, such as praying to Jesus or taking part in Christian rites. Gently telling your family what you can and can't do usually goes better than staying silent.

How Muslims view your Christian background

Muslims honour Jesus (Isa) as one of the greatest messengers of Allah, and Mary (Maryam) as one of the most righteous women. Many converts find that the faith, prayer and care for others they learned as Christians carry straight into Islam. What changes is who you worship: Allah alone. See Do Muslims and Christians believe in the same God?