Therefore, the capacity would depend entirely on:
* If a refrigerator was installed: Was one added? If so, what size and type?
* Type of refrigerator: A small portable cooler might hold a few liters, while a larger, permanently installed unit could hold many more.
To find out the capacity, you'd need to specify the van's year and check any available documentation about modifications done to that specific vehicle, or measure the refrigerator's interior volume if one is present.