Glenda --
Thanks for offering this question!
Since the regiment mentioned came from Memphis TN, an area under Federal control in 1863, conscripts were assigned to build up strength. As groups of conscripts arrived from assembly points, they were assigned to brigades and distributed on an as-needed basis. It would be difficult to reconstruct exactly what was decided on the spot.
Copies of military service files and pension applications are available here. We're always happy to answer questions.