Troop ship : WWII

There were several troopships in the Moore-McCormack Line.

To find out which ship the person was on, but you may be able to determine that by obtaining the records for his unit ( for example: 789th AAA) from the National Archives in College Park, MD.
These records may indicate which troops were on which ships.

National Archives and Records Administration, 8601 Adelphi Road, College Park, MD 20740-6001.-----------
Modern Military Records (NWDT2)- telephone (301) 837-3510

List of troopships in Moore-McCormack Line:

Brazil, later Virginia
Cape Victory
Marine Angel
Marine Jumper
Marine Lynx
Marine Phoenix
Mormacdove
Mormachawk
Mormacmoon, later Exchester
Mormacport, later Sea Fox
Mormacsea
Mormacwren
Sea Flier
Sea Pike
Sea Quail
Uruguay, later California

Another approach to determining the troopship name may be possible if you know the date the person traveled on the ship.
If you do, then you may be able to determine the ship name from convoy records of the Tenth Fleet Files, which are also held at the National Archives in College Park.

Once you have a name, you should be able to find a history and picture of the troopship in the following publication:

Charles, Roland W. Troopships of World War II. Washington, DC: Army Transportation Association, 1947.