First, let's look at the verse in context:
8 Therefore repent, and be baptized in the name of Jesus, and lay hold upon the gospel of Christ, which shall be set before you, not only in this record but also in the record which shall come unto the Gentiles from the Jews, which record shall come from the Gentiles unto you.
9 For behold, this is written for the intent that ye may believe that; and if ye believe that ye will believe this also; and if ye believe this ye will know concerning your fathers, and also the marvelous works which were wrought by the power of God among them.
Mormon, in what ends up being the last few verses he authors, offers the remnant of "this people" a few words of advice (see verses 2-5). His final words of advice are about laying hold upon the Gospel of Jesus Christ. "This" refers to his record, the Book of Mormon, and "that" refers to the Bible.
Notably, we get a glimpse into why the Book of Mormon sounds very biblical in its literary style, there in verse 9:
For behold, this is written for the intent that ye may believe that; and if ye believe that ye will believe this also;They are written to complement each other.