Brothers and Sisters, these are the following reasons why Mary is the Ark of the Covenant in the New Testament and its connection with the Ark of the Covenant in the Old Testament:
Old Testament:
God told Moses to make an Ark of the Covenant where his commandments will be placed (Ex 25:10-22).
New Testament:
Mary was chosen as the Ark of the Covenant because the Lord chose her to be the mother of the Messiah and she was highly favored for the Lord is with her and blessed among women (Lk 1:26-31).
Take note that she conceived in her womb our Lord Jesus Christ, the word that was made flesh and dwelt among us (Jn 1:14).
Old Testament:
The Ark of the Covenant was used in the procession and even King David leaped and danced for joy when it came into his city. He also offered burnt offerings and peace offerings before the Lord (2 Sam 6:16-17).
New Testament:
When Mary met Elizabeth (the mother of St. John the Baptist), her baby leaped in her womb and was filled with the Holy Spirit (Lk 1:36-41).
In short that the Ark of the Covenants in the Old and New Testament are connected with each other because this is part of God’s plan for salvation and also the law was given by Moses, but the grace and truth came from Jesus Christ (Jn 1:17, Mat 5:17).