The 1837 edition changed the demonstrative those in “all those signs and wonders” to these, probably unintentionally. Joseph Smith did not mark the change in 𝓟 when he edited the text for the 1837 edition. As described under Mosiah 28:1 and Alma 3:25, there are many mix-ups of these and those in the early transmission of the text. In each case, the critical text will follow the earliest extant reading, thus those here in Helaman 15:3. Since both the printer’s manuscript and the 1830 edition have those, the original manuscript (not extant here) undoubtedly did too. Elsewhere in the text, we have examples of either those or these with “signs and wonders”:
The original text in Helaman 15:3, “all those signs and wonders”, agrees with the two examples in 3 Nephi in that the demonstrative those is not repeated; the these is repeated in Helaman 14:28 (“these signs and these wonders”).
Summary: Restore in Helaman 15:3 the demonstrative those (“all those signs and wonders”), the original reading; this reading agrees with the nonrepeated those in 3 Nephi 1:22 and 3 Nephi 2:1.