MLA
Burns, Cardie. Letter from Cardie Burns (Eminence College, Eminence, Kentucky) to Mr. Chester Pierce Informing Him That Pierce's Mother and Sister Is in Eminence, Kentucky - December 5, 1864. 1864. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 1, Folder 44. https://digital.library.emory.edu/purl/945cc2fs0d-cor.
APA, 6th edition
Burns, C. (1864). Letter from Cardie Burns (Eminence College, Eminence, Kentucky) to Mr. Chester Pierce informing him that Pierce's mother and sister is in Eminence, Kentucky - December 5, 1864 (Box 1, Folder 44) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/945cc2fs0d-cor.
Chicago
Burns, Cardie. “Letter from Cardie Burns (Eminence College, Eminence, Kentucky) to Mr. Chester Pierce Informing Him That Pierce's Mother and Sister Is in Eminence, Kentucky - December 5, 1864.” Letters (correspondence). Civil War Collection, 1864. Box 1, Folder 44. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/945cc2fs0d-cor.