Do I Need to Know What an ISRC or UPC Code Is?
They are codes that the music industry uses for stuff and things. Sometimes.
DistroKid takes care of these things automatically (generates them, associates them with your music, etc.) so you don't have to think about it. Focus on your music and leave the technical to us.
If you do know what these things are, and have specific questions about UPC or ISRC, here's more info.