As a relative, you can request copies of his military records, which usually contain this information. I just received my Father's records and the medals were listed within. The cost was $60.00 but well worth the information I received.
This is the link where you can find the request form. Sincerely, Colleen Holth
http://www.archives.gov/st-louis/military-personnel/public/veterans-and-next-of-kin.html