Arguing with Protestants that insist Catholics prove some part of the Faith with references to the Bible is a waste of time. The Faith isn’t dependent on Sacred Scripture; Sacred Scripture depends upon the Faith!
Trying to answer such questions as “where is Purgatory mentioned in the Bible?” is pointless - Purgatory comes to us from the same source as the Bible itself: the Traditions of the Church. If the Protestant asking such a question were honest with himself, he would realize that accepting the Bible as Sacred Scripture, but not Purgatory as Sacred Tradition is contradictory. The Church, source of both Sacred Scripture and Sacred Tradition, is either infallible, or it is not. If you throw out Sacred Tradition, you should be prepared to throw out Sacred Scripture (all of it, not just a few parts!)
So, as a note to any Protestant that may be reading this post: stop challenging the Catholic Faith by question extra-Biblical Tradition, and instead challenge yourself and your acceptance of parts of Sacred Tradition, which has brought to you Sacred Scripture, “the Bible”. Either you accept the infallibility of the Church, accept the Christian Faith, and become a Catholic (Universal) Christian, or you reject it outright and abandon your heresies and apostate yourself from the Faith entirely. Those are the only logical outcomes.