Here the earliest text has the subordinate conjunction that before “in this year”. The 1874 RLDS text accidentally omitted the that here, but it was restored to the RLDS text in 1908. The normal situation is to have a that between “it came to pass” and “in this year” (at least six other times in the text). There is one example of a that after this prepositional phrase: “and it came to pass also in this year that there were some dissenters which had gone forth unto the Lamanites” (Alma 63:14). And there is one example where there is no that at all: “and now it came to pass in this year … there were a great division among the people” (4 Nephi 1:35). Finally, there is one unclear case with variation in the earliest textual sources; see under Mormon 1:8 for discussion of that case.
Summary: Maintain in Helaman 11:3 the that between “it came to pass” and “in this year”, the reading of the earliest extant source (𝓟 in this case).