Hi Shivani,
The best way to retrieve all values of a picklist is to use DescribeEntitiesMessage specifying the pickup entity name in TypesNames. The result EntityDescriptions should contain the PickupEntityDescription with the Pickups collection.
If you don't know the pickup entity name, use DescribeEntitiesMessage _on the entity containing the pickup field (_Project in this case), and check the ReferencedEntities property in the appropriate FieldDescription within the Fields collection.
Hope this helps,
Ophir