What’s my repair ID

We are end users like you. We cannot know. If you sent the device to Apple, you will have received an email from them with the number included. Looks like this:

If you have multiple email accounts, check them all. Normally Apple sends to the email address associated with your Apple ID.

If you cannot find the email you will ned ot call Apple support. They will not see your question here.

If you used an independent service provider, Apple cannot help.