As explained under 1 Nephi 3:2, Joseph Smith revised nearly half the instances of “in the which” when he edited the text for the 1837 edition, usually by omitting the the. Here in Mormon 1:11 is one instance where Joseph left “in the which” unchanged; in this case, the the was later removed in the 1849 LDS edition. The LDS text has maintained the expected reading without the the, but the critical text will restore the original “in the which”. For a complete discussion, see under in the which in volume 3.
Summary: Restore the original instance of “in the which” in Mormon 1:11 and elsewhere in the text where the the has been omitted (usually by Joseph Smith in his editing for the 1837 edition).