MLA
Richards, Henry. Letter from Henry Richards to His Mother (Savannah, Georgia) - April 24, 1864. 1864. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 5, Folder 62. https://digital.library.emory.edu/purl/569z08kqt3-cor.
APA, 6th edition
Richards, H. (1864). Letter from Henry Richards to his mother (Savannah, Georgia) - April 24, 1864 (Box 5, Folder 62) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/569z08kqt3-cor.
Chicago
Richards, Henry. “Letter from Henry Richards to His Mother (Savannah, Georgia) - April 24, 1864.” Letters (correspondence). Civil War Collection, 1864. Box 5, Folder 62. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/569z08kqt3-cor.