I suggest you purchase Beginning Apologetics 2 **How to Answer Jehovah’s Witnesses and Mormons ** from San Juan Catholic Seminars
I thoroughly recommend the series. They are easy to read without going into the teaching of JWs and LDS too deeply, so you don’t need to be a theologian to understand them.
After that, there are many other resources available to refute their beliefs.
The ones who come to your door are trained what to say and how to say it. Their presentations are well-rehearsed and often memorised to enable them to “confuse” you.
They will not accept any tracts or similar from you so I just usually tell them I am a Catholic because of my study of early Church history, especially the writings of the Apostolic and Early Church Fathers whose writings are available online. Especially the writings of Polycarp, Clement of Rome and Ignatius of Antioch, who were taught directly by the apostles themselves.
If Mormons try to bring up the Great Apostasy, tell them that they need to read the ECF as they will find that if it happened, it must have happened that Jesus founded an apostate church as we have the same Church today with the same teachings and doctrines. That is simply not logical.
Telling them you are a Catholic won’t do anything except get them excited because many of their converts have come from the ranks of badly catechised Catholics and they are trained what to say to you.