MLA

Backus, Isaac, 1724-1806. Day book. Box 2, folder 4, item 2629216. 1760–1769. https://collections.library.yale.edu/catalog/33499961.

APA, 6th edition

Backus, Isaac, 1724-1806. (["Box 2, folder 4, item 2629216"])(1760–1769)[Day book]. https://collections.library.yale.edu/catalog/33499961.