Steve, according to Fold3 they were at Camp Florida, Va in November 1861. https://www.fold3.com/image/271/70993322

Co A shows at Camp Moore on 7th July 1861 https://www.fold3.com/image/271/70993340 but at Camp Bienville near Centreville VA from 7 July to 31 Aug 1861. B, C, D, G, H, I and K similar.

Co E shows at Camp Moore 8 July 1861 https://www.fold3.com/image/271/70993781

So sometime after 7/8 July and before 31 Aug 1861 is the best that I can find at the moment.

Alan Thrower
England