There is the Apostolic Constitution of Pius XII: Defining the Dogma of the Assumption which describes the Dogma.
Understanding the Assumption is dependent upon the other three Marian Dogmas and is difficult to treat alone. An understanding of Mary as the Mother of God is the first step, followed by the Perpetual Virginity, and then the Immaculate Conception.
You will not find a verse that specifically says “Mary was assumed into heaven.” But understanding the types of Mary such as the Ark of the New Covenant and the New Eve are helpful in understanding Mary’s proper role.
Here are some verses to consider:
Mt 27:52-53 "52 the tombs also were opened, and many bodies of the saints who had fallen asleep were raised, 53 and coming out of the tombs after his resurrection they went into the holy city and appeared to many.
If the saints of old were raised, is it unbiblical to think that Jesus would not raise His mother?
People being assumed into heaven is not unbiblical:
Gen 5:24 “24 Enoch walked with God; and he was not, for God took him.”
2 Kings 2:11 “11 And as they still went on and talked, behold, a chariot of fire and horses of fire separated the two of them. And Eli’jah went up by a whirlwind into heaven.”
Jude 1:9 "But when the archangel Michael, contending with the devil, disputed about the body of Moses, he did not presume to pronounce a reviling judgment upon him, but said, “The Lord rebuke you.”