MLA
Forbes, Murray. Letter from Forbes Murray (Norwood, Bedford County, Virginia) to "My Dear Mother" - July 10, 1863 [Photocopy]. 1863. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 3, Folder 26. https://digital.library.emory.edu/purl/1913n5tc47-cor.
APA, 6th edition
Forbes, M. (1863). Letter from Forbes Murray (Norwood, Bedford County, Virginia) to "My dear Mother" - July 10, 1863 [photocopy] (Box 3, Folder 26) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/1913n5tc47-cor.
Chicago
Forbes, Murray. “Letter from Forbes Murray (Norwood, Bedford County, Virginia) to ‘My Dear Mother’ - July 10, 1863 [Photocopy].” Letters (correspondence). Civil War Collection, 1863. Box 3, Folder 26. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/1913n5tc47-cor.