You have to unpack the materials inside Unity By clicking on the asset (Area 1 and you will find unpack materials and unpack textures options if you have textures you can unpack those also) and then change then change the rendering mode to transparent and change the alpha value in color 👍🏻
#How to create a transparent material in blender
chrome nimbus
If you are looking from top you dont need more faces but If the camera will be in this position you should consider adding solidify modifier or extra faces to those bins or else Unity will render them from only inside