I need some help. I've just had a client place an order for the Compiled Military Service Record and Pension Application of:

Soldier's Full Name: John Welch b.1833 Father Thomas F. Welch
Soldier's Unit Info: 1862 Co C, 42 Ark Infantry, Iuka, Corinth, Port Hudson

I'll be asking this customer some additional questions, but can anyone decipher what unit this might be?

Jim