The concept of a pre-existence for humans is unbiblical. Mormons believe that there was a great war in heaven. We fought on the side of Lucifer, or Jesus, two competeing brothers. Those who were neutral were cursed with dark skin because they were cowards. The Bible testifies that we were created in our mother's womb. We had no opportunity to do good or evil before we were born.
For the children being not yet born, neither having done any good or evil, that the purpose of God according to election might stand, not of works, but of him that calleth; Romans 9:11
"Thus saith the LORD, thy redeemer, and he that formed thee from the womb, I [am] the LORD that maketh all [things]; that stretcheth forth the heavens alone; that spreadeth abroad the earth by myself; That frustrateth the tokens of the liars, and maketh diviners mad; that turneth wise [men] backward, and maketh their knowledge foolish; " Isaiah 44:24
“This shall be written for the generation to come: and the people which shall be created shall praise the LORD.” Psalm 102:18
Did not he that made me in the womb make him? and did not one fashion us in the womb? Job 31:15
Thus saith the LORD that made thee, and formed thee from the womb, [which] will help thee; Fear not, O Jacob, my servant; and thou, Jesurun, whom I have chosen. Isaiah 44:2
-"God never had the power to create the spirit of man at all."
"We say that God himself is a self-existent being.. Man does exist upon the same principles.. The mind or intelligence which man possesses is co-equal with God himself.. The intelligence of spirits had no beginning, neither will it have an end.. There never was a time when there were not spirits; for they are co-equal with our Father in heaven.. All the fools and learned and wise men from the beginning of creation, who say that the spirit of man had a beginning, prove that it must have an end.. I might with boldness proclaim from the house-tops that God never had the power to create the spirit of man at all, God himself could not create himself" Joseph Smith, Teachings of the Prophet Joseph Smith, pp. 352-4).