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.
https://www.kbb.com/whats-my-car-worth/
Please feel free to post any additional details or questions in the comment section.
The "Vehicle Cost" is requesting "the fair market value of the vehicle at the time when you placed it in service." This is a 1991 Ford Explorer, placed in service in 2003. How & where do I go to calculate that?
Since the vehicle was twelve years old when you put it into service, it wouldn't be worth much unless it had major improvements done to it. So, you can assign a minimal value to it. Also, it would have been fully depreciated by now, so the number you assign should be of little consequence to what you are doing now.
"Minimal Value" is not helpful, as you need to assign it a value. I am in a similar situation, I traded in my vehicle from 2011, that didn't enter service until 2017, for a new 2022. Now, TurboTax is asking for the fair market value of my 2011 when it entered service in 2017. How are you supposed to calculate this? I would assume the IRS frowns upon people randomly assigning value to an asset with just the justification of "it's old". Minimal value could mean very different things to different people.