MLA
Miles, James Jefferson. Letter from James Jefferson Miles to His Sister, Elizabeth Fuller. Miles Served in the 3rd Mississippi Infantry Battalion and Later the 45th Mississippi Infantry Regiment - January 16, 1863. 1864. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 5, Folder 17. https://digital.library.emory.edu/purl/0171vhhnhf-cor.
APA, 6th edition
Miles, J. J. (1864). Letter from James Jefferson Miles to his sister, Elizabeth Fuller. Miles served in the 3rd Mississippi Infantry Battalion and later the 45th Mississippi Infantry Regiment - January 16, 1863 (Box 5, Folder 17) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/0171vhhnhf-cor.
Chicago
Miles, James Jefferson. “Letter from James Jefferson Miles to His Sister, Elizabeth Fuller. Miles Served in the 3rd Mississippi Infantry Battalion and Later the 45th Mississippi Infantry Regiment - January 16, 1863.” Letters (correspondence). Civil War Collection, 1864. Box 5, Folder 17. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/0171vhhnhf-cor.