Here Oliver Cowdery initially wrote “should be filled” in 𝓟; then virtually immediately he corrected the should to shall (there is no change in the level of ink flow for the supralinear shall ). Either reading works, although the should seems more expected. There are a couple of cases in 3 Nephi 9 where Oliver initially wrote should in 𝓟 rather than the correct shall; for discussion of these cases, see under 3 Nephi 9:5, 7. Most likely, Helaman 7:9 read shall in 𝓞 (which is not extant here), especially since there is nothing wrong with should and thus there would have been no motivation for Oliver Cowdery to consciously emend should to shall.
Summary: Accept in Helaman 7:9 the corrected reading in 𝓟 with the modal shall: “that my soul shall be filled with sorrow”.