I believe that would be the Department of North Virginia G. O. No. 5-18. Believe it would be found at the National Archives in Washington, D. C. and you would have to visit the Old Army Archivists there to locate and view.
This may be a site to start with.
War Department Collection of Confederate Records
https://www.archives.gov/research/guide-fed-records/groups/109.html#109.9.1