The original manuscript reads “those prisoners of war”. Oliver Cowdery accidentally changed those to these when he copied the text from 𝓞 into 𝓟. We have already seen numerous examples of scribes and typesetters mixing up these and those while copying the text (for those examples where Oliver made the error, see under Alma 3:25). For each case of these versus those, the critical text will follow the reading of the earliest textual sources.
Summary: In accord with the reading of the original manuscript, restore those in Alma 57:16: “those prisoners of war”.