Here some pix, difficult to do inside the case because of the brightness, I took the pix with the removed parts on the table .
Left of the green panel, the light grey spot is the open circle which maintains the panel in place.
Right of the green panel, the bright grey spot is the metal piece under the green panel which maintains the button in place.
Once the panel button out,
you will see the metal keeping the button in place and underneath the button itself
Now you only have to put back the parts in the other case in the reverse order.
I use this to extract the parts :