MLA
Wilkes, John K. Letter from John K. Wilkes (Camp Fisher near Dumphreys, Virginia), to His Father. In the Letter, Wilkes Describes Battle Fought and Casualties Incurred - February 15, 1862. 1862. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 7, Folder 25. https://digital.library.emory.edu/purl/26663xsk5h-cor.
APA, 6th edition
Wilkes, J. K. (1862). Letter from John K. Wilkes (Camp Fisher near Dumphreys, Virginia), to his father. In the letter, Wilkes describes battle fought and casualties incurred - February 15, 1862 (Box 7, Folder 25) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/26663xsk5h-cor.
Chicago
Wilkes, John K. “Letter from John K. Wilkes (Camp Fisher near Dumphreys, Virginia), to His Father. In the Letter, Wilkes Describes Battle Fought and Casualties Incurred - February 15, 1862.” Letters (correspondence). Civil War Collection, 1862. Box 7, Folder 25. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/26663xsk5h-cor.