Hello Maddiechilds77,
Thanks for reaching out to Apple Support Communities. Upon review of your post, it seems that you can’t locate the return label to send back a package to Apple. We can see why you’d want this taken care of, so let us help from here! On the package you received the replacement in, you may be able to locate the return label beneath the existing label on the parcel.
If the return label is still missing, we recommend that you contact Apple Support directly. Depending on your region, you may be able to reach them here: Get Support.
Thank you for participating in the Apple Support Communities and have a wonderful day.