In this passage, the 1837 edition replaced the conjunction and with that, probably accidentally since here either reading will work, providing we interpret the that as meaning ‘with the result that’. The and seems more natural in this particular passage. The textual history has quite a few examples of the resultive that being replaced by the conjunction and (the opposite of the change here in Alma 16:8), as in the following example when Oliver Cowdery initially wrote and in 𝓟 rather than the correct that:
For other examples of this tendency, see the discussion under 1 Nephi 11:29.
Here in Alma 16:8, the 1920 LDS edition restored the and by reference to the 1830 edition. The RLDS text has retained the 1837 reading, even though 𝓟 itself has only the and (that is, without any later alteration in 𝓟 of the and to that).
Summary: Maintain in Alma 16:8 the conjunction and before the resultive clause “they took their brethren”.