Dear Sir,
Milton G. McDonald did serve in the First (Carter's) Tennessee Cavalry Regiment. Below is a link referring to the regimental history listed in "Tennesseans in the Civil War, Part I", pages 49-52.
http://www.tngennet.org/civilwar/csacav/csa1carter.html
Please let me know if you have any questions.
Respectfully,
Gerald D. Hodge, Jr.
Warner Robins, Georgia
War Between the States Historian
Historian: 39th Georgia Volunteer Infantry Regiment
http://39thgavolinfrgt.homestead.com/39thHomepage.html
Descendent of soldiers in the 39th Georgia and the 2nd (Ashby's) Tennessee Cavalry