You have to print 36 copy of the drawer.stl and glue them together to the drawer_front's. Or put the front on top of the drawer in your slicer if your printer is capable of really good bridging.

If you want the color change in the drawer_front you have to inject the change filament (M600) command above 0.6mm in your gcode.
(You might have to enable change filament in your firmware.)