Why is my iPhone showing unknown part

A message about a non-genuine part is discussed in this support document: iPhone parts and service history - Apple Support

An Unknown Part message appears if the part installation is incomplete or if the part:

- Was replaced with a nongenuine part (e.g., you had it repaired with a third party service that did not use an Apple component)

- Was already used or installed in another iPhone

- Isn't functioning as expected

If the reason isn't immediately apparent, go to this page to find your nearest Apple Authorized Service Provider (AASP) or Apple Authorized Distributor (AAD) --> Find Locations

How to make a Genius Bar appointment

1. Go to Genius Bar Reservation and Apple Support Options - Apple

2. Go to "Get hardware help".

3. Select your hardware and continue selecting options requiring replacing parts until you see "Bring in for Repair"

4. Sign in with your Apple ID

The question is what is the unknown storage part on the iPhone?

godFFAAA3 wrote:

The question is what is the unknown storage part on the iPhone?

No, that wasn't the question. Since your question is different I suggest you start your own topic about storage.