You need to appeal the rejection using an explanation that App Revbiew can understand. For example, in your post you wrote "3D row scanned model" - what is that? You need to be clearer in your communications.
Is the "3d row scanned model" being used in the app? If so, it falls under 3.1.1 and you must use IAP. If the "3d row scanned model" is not being used in the app then explain to app review that the purchase does not unlock any features or functionality within the app and is not used in the app.
3.1.5 does not necessarily apply to 'digital goods' - it appleis to physical goods and services - and I suspect that "3d row scanned model" is a digital good.
If your 3D models are used inside the app, then you must use IAP but if your app is just a shop and the 3D models are used outside the app, then you should send an appeal. Explain to the reviewer what your models represent, what they are used for, and don't forget to mention that your app is just a store and the models are not used inside the app.