MLA
Couch, Jackson. Letter from Jackson Couch to His Wife, Arminda Couch - October 28, 1862. 1862. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 2, Folder 29. https://digital.library.emory.edu/purl/962f7m0dgp-cor.
APA, 6th edition
Couch, J. (1862). Letter from Jackson Couch to his wife, Arminda Couch - October 28, 1862 (Box 2, Folder 29) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/962f7m0dgp-cor.
Chicago
Couch, Jackson. “Letter from Jackson Couch to His Wife, Arminda Couch - October 28, 1862.” Letters (correspondence). Civil War Collection, 1862. Box 2, Folder 29. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/962f7m0dgp-cor.