ISRC and UPC are codes used in the music industry. They help identify your release and tracks.
DistroKid has been appointed by the US ISRC Agency to assign ISRCs, and will automatically generate new DistroKid ISRC codes for every song you upload. It's free and automatic, and you'll receive 100% of earnings.
If you have a Musician Plus or Ultimate subscription plan, you can use your own ISRC's when uploading.