Dear Ms. Robinson,
Thank you for posting your request on History Hub!
To seek the military records of your grandfather, please begin by requesting his Official Military Personnel File (OMPF). OMPFs and individual medical reports for those who served in the U.S. Armed Forces and who were separated from the service prior to 1955 are in the custody of NARA's National Personnel Records Center in St. Louis. In many cases where Army and Army Air Corps personnel records were destroyed in the 1973 fire, proof of service can be provided from other records such as morning reports, payrolls, and military orders, and a certificate of military service will be issued. Navy and Marine Corps OMPFs were not affected by the fire. Please complete a GSA Standard Form 180 and mail it to NARA's National Personnel Records Center, (Military Personnel Records), 1 Archives Drive, St. Louis, MO 63138-1002.
We hope this is helpful. Best of luck with your family research!