Here Oliver Cowdery initially wrote “to the city of Judeah” in 𝓟, but almost immediately he corrected the preposition to at, the reading in 𝓞. The critical text will continue with the original preposition at. For a complete discussion of the variation between to and at in the history of the text, see under 1 Nephi 17:14.
Summary: Maintain in Alma 56:15 the original preposition at in the clause “when I arrived at the city of Judea”.