MLA
Couch, Jackson. Letter from Jackson Couch (Madison, Mississippi) to His Wife, Arminda Couch, and Children - January 3, 1864. 1864. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 2, Folder 29. https://digital.library.emory.edu/purl/4644qrfk6v-cor.
APA, 6th edition
Couch, J. (1864). Letter from Jackson Couch (Madison, Mississippi) to his wife, Arminda Couch, and children - January 3, 1864 (Box 2, Folder 29) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/4644qrfk6v-cor.
Chicago
Couch, Jackson. “Letter from Jackson Couch (Madison, Mississippi) to His Wife, Arminda Couch, and Children - January 3, 1864.” Letters (correspondence). Civil War Collection, 1864. Box 2, Folder 29. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/4644qrfk6v-cor.