If you're looking for the ISRC of a track released via Beatchain, find the release in your release list, then click the eye button on the track (as in the image below) then click 2. Copyright. You should be able to see your ISRC for that track.
If you need to find your ISRC to move releases TO Beatchain, we recommend asking your old distributor for the ISRC codes for each track.
See also: What is an ISRC?