That's not a familiar unit title. I'll guess you're asking about the 3rd Alabama Reserve Regiment, which was a senior reserve command.

Sometime just before General Taylor surrendered all Confederate troops in his department, the two junior reserve regiments were renumbered 62nd and 63rd Alabama. The basis for this designation had to do with seventeen-year old reserves all becoming eighteen since the spring of 1864. Of course senior reserves became older, and I've read nothing convincing that these commands ever received regular designations. A couple of surrender entries appear in the Alabama miscellaneous records for the 64th Alabama, but I haven't matched them to a previously identified unit.

What's the source of your information?