MLA
Couch, Jackson, and M. Couch. Letter from Jackson Couch and M. Couch to Malissa[?]. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 2, Folder 29. https://digital.library.emory.edu/purl/40644j10mw-cor.
APA, 6th edition
Couch, J., & Couch, M. Letter from Jackson Couch and M. Couch to Malissa[?] (Box 2, Folder 29) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/40644j10mw-cor.
Chicago
Couch, Jackson, and M. Couch. “Letter from Jackson Couch and M. Couch to Malissa[?].” Letters (correspondence). Civil War Collection, n.d. Box 2, Folder 29. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/40644j10mw-cor.