First, how do you set the device up at all? (Android app, iOA app, CLI, serial, …)
To claim the device you don’t need the claim code but the device ID.
And this you get in Listening Mode via CLI particle device identify
or via any serial terminal program by sending i
to the device.
But if you really want the claim code, the docs do tell
https://docs.particle.io/reference/api/#create-a-claim-code
So it is easy - when know the docs and use the search features in the docs and this forum.