RV blue book values are available from NADA Guides. They list your camper under the manufacturer name [Mallard by Fleetwood].
Using this information, you can follow these steps to find a blue book value by adding the model along with any option/accessories that may be included.
There were many Mallard by Fleetwood models, so we have used [240BH] as an example to provide step by step directions below:
Select = [RVs]
Type = [Travel Trailers / 5th Wheels]
Manufacturer = [Mallard by Fleetwood] < start here
Year = 
Model = [240BH]
Option = [Select]
[Get Base Pricing]
Suggested List Price = $17860
Low Retail = $4450
High Retail = $5360