I really do not know and should know to leave it alone
Regardless.
Yes, Vicksburg was the Exchange Point for the Western Armies.
Camp Fiske, I think, the location was on the Rail Road a couple of miles eastward from Vicksburg. Today's location Beechwood Community, out near Warren Central High School & Hinds Community College.
I am under the impression that there is very little information known about it.
However, it operated from the beginning to the end.
The Yankee prisoners that were on the Sultana came through Camp Fiske.
Also, there were no Exchanges at Vicksburg from the time General Sherman arrived about December, 1862 (Battle of Chickasaw Bayou.) until early 1865. (Two years plus.)
There were some / many / a large number of prisoners that passed through.
I saw something on maybe the Arkansas Message Board a few days past where several Confederate Soldiers captured at the Salt Peter mine in Arkansas were in Vicksburg awaiting Exchange and got caught up in the Siege. (Do not understand it but.)
This is a subject that I would encourage to be investigated