MLA
Wilkinson, F. M. Letter from F. M. Wilkinson (Camp Pemberton near Savannah, Georgia) to His Father, C. R. Wilkinson - April 14, 1864. 1864. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 7, Folder 27. https://digital.library.emory.edu/purl/4472v6wxqz-cor.
APA, 6th edition
Wilkinson, F. M. (1864). Letter from F. M. Wilkinson (Camp Pemberton near Savannah, Georgia) to his father, C. R. Wilkinson - April 14, 1864 (Box 7, Folder 27) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/4472v6wxqz-cor.
Chicago
Wilkinson, F. M. “Letter from F. M. Wilkinson (Camp Pemberton near Savannah, Georgia) to His Father, C. R. Wilkinson - April 14, 1864.” Letters (correspondence). Civil War Collection, 1864. Box 7, Folder 27. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/4472v6wxqz-cor.