Unity has only simple transform tools that cant handle this case. Blender can be used to prepare the object for this.
ShapeKeys are the way to go:
Setup your object either totally "full" or "empty"
Create a basis and a key (in Object Data properties)
Select key and edit/scale your mesh with Shift + X to full/empty in Edit Mode.
Export to ...
So, let me preface by saying, its been a hot minute since I worked with Unity, and they do update things, so some things might be different.
Unity has really good documentation so id recommend checking that out. https://docs.unity3d.com/Manual/index.html
Unity Learn has tutorials that will get you started and show you how to set up your file structure ...