Mormons do not pray to Mary. Statues are art, and, as with any other form of art, might be found in an individual building or home, usually in a nativity setting.
There are several aspects of Mormon beliefs that must be understood before this question can be answered. The first is that Mormon beliefs do not include the trinity. While they believe in God, Jesus, and in the Holy Ghost, they do not teach that they are the same being. They are three very distinct beings, wholly unified in purpose. For more on this, please read:
How Could Jesus Pray to Himself?
The second important point of Mormon doctrine is that we lived with God before we were born. God created our spirits and we lived with Him for a time before coming to earth.
Toddlers are taught, in their very first church class, this little rhyme:
Heavenly Father knows me
And what I like to do.
He knows my name and where I live.
I know He loves me, too.
Mormons believe this, and believe God knows them and loves them enough to recognize and notice their voices, and that He can hear and answer every prayer, no matter how many are coming through at any one time. This is a part of His divinity.
Mormons pray to God through Jesus Christ. Jesus was given the role of Intercessor by God. When Jesus Christ offered the Intercessory Prayer, we saw how He was able to pray on our behalf to the Father.
Several scriptures in the Bible promote Jesus’ role as our advocate or intercessor, including Timothy’s explanation that there is only one mediator:
5 For thereis one God, and one mediator between God and men, the man Christ Jesus; (1 Timothy 2)
Mary is very important in Mormon theology. prior to her birth, and that her mission was foretold by prophets. Isaiah said, “14 Therefore the Lord himself shall give you a sign; Behold, a virgin shall conceive, and bear a son, and shall call his name Immanuel.” Isaiah 7:14
The Book of Mormon also foretells Mary. Both Lehi and his son Nephi, the first two Book of Mormon prophets, saw Mary in visions and knew she would be the mother of God’s only begotten Son.
“As there is only one Christ, so there is only one Mary. And as the Father chose the most noble and righteous of all his spirit sons to come into mortality as his Only Begotten in the flesh, so we may confidently conclude that he selected the most worthy and spiritually talented of all his spirit daughters to be the mortal mother of his Eternal Son.” (Bruce R. McConkie, Doctrinal New Testament Commentary, Bookcraft, Inc., 1965, vol. 1, p. 85.)
We know that Mary had lived a highly moral life in order to be allowed to carry out this great assignment. We can presume she was intelligent and her responses to her calling tell us she knew the scriptures well.
Jesus came to earth as a baby, not a grown man. He did not begin with a full knowledge of who He was or a complete memory of His life prior to His birth. It would have been Mary’s role to train Him in the ways of life and to help Him become the type of person who could and would carry out His eternally significant mission. We can, therefore, presume she was a wise and capable parent, and that she never lost sight of her role in God’s plan for the earth.
For these reasons, and because of the tremendous sacrifices she made and the suffering she endured as she witnessed the treatment and death of her firstborn Son, Mormons honor Mary.
She is often used as an example of a woman of faith, sacrifice, and obedience. In lessons on motherhood, she is usually the first example offered. Mormons look to her to show them the way to live their own lives, but their relationship with God is a direct one. Mormons pray to God, through Jesus. They don’t feel the need to ask someone else to intervene on their behalf, because they believe God loves them enough to hear them. While they might ask friends to pray for them, this does not replace praying to God themselves. Being prayed for by others helps us to connect to one another, but even if only one person prayed for himself, that pray would be heard and answered.
Some have asked if we have statues of Mary. Mormon chapels do not have artwork of any kind in the actual chapel where the service is held. The chapels are extremely simple and free of any decoration except for occasional flowers. However, the buildings-hallways, offices, and classrooms– do have paintings, and some have statues. The statues serve only as decoration and are not used in any way in the worship services. They serve only as teaching aids or reminders of important aspects of gospel teaching.
Art plays an important part in Mormon life as a tool for teaching. Teachers are encouraged to use it to help emphasize aspects of the story or principle being taught, to hold attention, or to invoke important thoughts or feelings. Mormons do not pray to statues or make use of them as part of their services, however. They are simply decorations or teaching tools. Statues of Mary are most often shown in context with her mission on earth as Jesus’ mother.