If it's available
Object > Expand Appearance
then Select > Select All
again, just to be certain everything is selected.
Repeat this step until Expand Appearance
is no longer available in the Object menu.
Object > Expand
Window > Pathfinder
To open the Pathfinder Panel (If it's not already open)
- Click the
Merge
button on the Pathfinder Panel
- Use the Direct Selection Tool (White arrow) to click a black object
Select > Same > Fill & Stroke
- Hit the Delete Key to remove black objects (you may need to hit Delete twice)
This leaves you with only the white objects.
For viewing purposes you may want to add a new layer with a color filled rectangle on it below the artwork layer and then lock that layer. This will allow you to see the white objects after the black has been removed. It can be helpful to use this color rectangle layer while performing the above operations. You can then merely delete the layer afterwards.