The ISRC (International Standard Recording Code) is the international identification system for sound recordings and music video recordings. Each ISRC is a unique and permanent identifier for a specific recording, independent of the format on which it appears (CD, an audio file, etc) or the rights holders involved. Only one ISRC should be issued to a track, and an ISRC can never represent more than one unique recording.
ISRCs are widely used in digital commerce by download sites and collecting societies. An ISRC can also be permanently encoded into a product as its digital fingerprint. Encoded ISRC provides the means to automatically identify recordings for royalty payments.
If your release has not already been distributed to any of the major platforms like (iTunes, Amazon, Spotify, etc.) then it won't have one. TuneGO will set an ISRC during the process of mastering a file at no cost to you.