Look up the fair market value of your car in a used-car guide such as the Kelley Blue Book. Find the make, model and year for your car and use the listed private-party value for the overall condition of the vehicle. For example, if the body is dented, the air-conditioning doesn't work and it has excessive mileage, it’s unreasonable to estimate the fair market value using the price for a car in “excellent” condition.
You'll also have to put your zip code in as the FMV will be adjusted to your local market.
(See the attached screenshot below. Click to enlarge.) This is your year, make and model with standard equipment in good condition in my locality.
Please feel free to post any additional details or questions in the comment section.