Go to: http://www.itd.nps.gov/cwss/soldiers.cfm
Enter:
Smith
J
Confederate
Mississippi
Several screens of names will appear. About the fifth (not sure) screen, you'll note "J.K. Smith" in "Grace's Company."
If you click on "Grace's Company," you will be taken to a page that has a link for a roster of all the men (about 96) in this company.
Howell (list of MS CS soldiers) says: "4th Corporal J.K. Smith, Capt. Grace's Company, MS State Troops, Independent Cavalry."
Military History of MS says: "Unattached (Cavalry) -- Grace's Company. Captain W.G. Grace, organized September 14, 1864, discharged March 15, 1865."
However, bear in mind that there is a Capt. Grace's company of independent cavalry and a Capt. Grace's company of independent infantry, so things can get mighty confusing!
A J.K. Smith filed for a CS Pension in 1922 in Neshoba County, MS, but did not state his unit on his application.
Wish I could have helped you more! I'm afraid I've just confused things even more! -- Jim Huffman, Gainesville Vols