In the publication:  STUDIES ON THE TESTAMENT OF MOSES, edited by George W.E. Nickelsburg, Jr., one in a series of studies of  SEPTUAGINT AND COGNATE STUDIES NO. 4, one of the contributors Dr. Sheldon R. Isenberg of the University of Florida,  in an Article entitled:  ON THE NON-RELATIONSHIP OF THE TESTAMENT OF MOSES TO THE TARGUMIM, who wrote (on page 84) :

"According He designed and devised me (Moses) and He prepared me before the foundation of the world" (TM  l:14)

He then commented on this quote:  
 "Two claims are made in this passage, the first involving Moses' pre-existence and the second more common claims of Moses mediating function between God and Israel.  The claim of Moses' pre-existence, of his being created before the world, is, as far as I know, to be found nowhere else in Jewish Literature."

It is common knowledge to all Mormons that Moses had a pre-existence, just as this is also true for all Mormons, and that those called to leadership positions were all Foreordained to those positions.   We read in Alma 13: 3,  "And this was the manner after which they were ordained-being called and prepared from the foundation of the world according to the foreknowledge of God on account of their exceeding faith and good works". 

One finds additional doctrine on being called and prepared before in the pre-existence be reading the rest of Chapter 13 of Alma.  Especially of interest is the phrase:  BEFORE THE FOUNDATION OF THE WORLD, in the quote by Isenberg from the Testament of Moses. This expression is found numerous times in Alma 13.  And the doctrine of being called and prepared is greatly elucidated in Alma 13. 

Isenberg's comment that this idea of Moses' pre-existence is as far as he knew to be found nowhere else in Jewish Literature.  Isn't the Book of Mormon "Jewish Literature"?   And Moses' most certainly was called and prepared for leadership position.  That is detailed in the first five chapters of the Pearl of Great Price where Moses stands out as the Head of a Dispensation of Gospel Principles and Doctrine.

If you do not have a Book of Mormon to check this out, have a Mormon Friend give you one.