Hi Sachin,
It appears that you're unable to add your iPhone Leather Wallet in Find My. The following article has information on adding the iPhone Leather Wallet into Find My: About the iPhone Leather Wallet with MagSafe
If you've followed those steps exactly, you could first see if restarting your iPhone helps resolve that error message: Restart your iPhone Restarting can seem like a simple step, but it can sometimes resolve unexpected issues. Another step you can also take that might help is to ensure your iPhone is fully updated:
If available, are you having issues adding other devices or items to the Find My app? We want to see if the issue is isolated only to your iPhone Leather Wallet or if its happening with multiple devices/items. If possible to test that, it can help us isolate and determine possible next steps.
Let us know how those steps or if you've already tried those.
Best wishes.