The Bible says:
John 10:16, And other sheep I have, which are not of this fold: them also I must bring, and they shall hear my voice; and there shall be one fold, and one shepherd.
The Book of Mormon teaches that a man named Lehi and his four sons, Laman, Lemuel, Sam, and Nephi left Jerusalem with their families and floated across the Atlantic Ocean and settled in the America’s in 600 B.C.
After Jesus’ resurrection, Jesus appeared to the Nephite and Lamanite people in the America’s and preached the gospel three days and three nights, then departed. This is how the Mormon gospel translates John 10:16 saying, that the Nephites and Lamanites of the Book of Mormon are the other sheep.
The Bible says:
In Genesis 17:7, God establishes an everlasting covenant with Abraham and the seed of Abraham for generations to come. That they (Israelites, Hebrews) would be His chosen people and He would be their God.
Being that Jesus was born a Jew (Hebrew). He started His ministries teaching the Jewish people (God’s chosen people). The Jews that believed in Jesus as the Messiah are the sheep that Jesus is talking about in John 10:11-15. The sheep that Jesus says, are not of this fold, are Gentiles. In Deuteronomy 7:3-4, God tells the Israelites they are not to marry or to associate with the Gentiles because they will turn the Israelites from the Lord their God and have them serve other gods. The Israelites believed that God’s Covenant with Abraham made them the only people that God want in His kingdom.
After Jesus’ death and resurrection and before Jesus ascended to heaven. He told the apostles. (Mark 16:15) “Go ye into all the world, and preach the gospel to every creature”. In Acts chapter 9, after Paul’s conversion on the road to Damascus, Jesus tells Paul to go and preach the name of Jesus to the Gentiles. Paul writes in Romans 2:10, “But glory, honour, and peace, to every man that worketh good, to the Jew first, and also to the Gentile”. Also in Acts chapter 10, the Apostle Peter has a vision from the Lord telling him that there is nothing that the Lord has made that is unclean and He tells Peter to go and preach the gospel to Cornelius and his household (Roman Gentiles). Then Peter realizes that Jesus wants him to preach to all the Gentiles.
The other sheep that are not of this fold are the Gentiles not Nephites and Lamanites of the Book of Mormon.
See also, Acts 11:18, 13:47, 14:27, 15:7, 26:20-23, Gal. 3:14, 2 Tim. 4:17, Col. 1:27.