Linda, a Col. Henry Gillum was commanding an outfit called Gillum's Regiment Louisiana Cavalry at the end of the war. I know nothing about this regiment, but there is no record that it ever served in Arkansas.

R. A. Kirk served in two different regiments from Prairie County. He served in Co. B, 2nd Regiment 30-Day Volunteers, between November 18 and December 18, 1861. He was also present in Co. G at the 1862 annual muster of the 50th Regiment Arkansas Militia, held in Prairie County on March 7-9, 1862. The 50th Regiment was the militia regiment of Prairie County. It was not present at Pea Ridge and took no active part in the war.

It's unlikely that this Prairie County man ended up in a Louisiana regiment, but I can't say for sure that he didn't since I have never seen any records of Gillum's regiment.