I am looking for software for my laptop that will compare Digital License Plate photos taken at two different times in a parking lot and save only the photos that show the same car plate, or will allow you to sort the photos into "pairs of the same plate numbers", showing the date and time.

I have a very small towing service and am contracted to some shopping centers that have a "Customer Parking Only 3 hour limit" on parking.
At present time we mark the tires with a paint marker crayon and go back three hours later and check tires for any with the marks still on the tire.
This is very time, and labor intensive and I am looking for a better way to monitor the lot.
I lost two court cases because the motorist asked the judge to make me prove with photographs the mark on the tire at the start and three hours later, which at the time I could not prove. The judge told me if I come back in front of him again I had better have photographic proof of the before and after marks on the tires. I asked the judge if a "Meter Maid" marked the tires on the street, would you make them show photographic proof of the mark on the tire? He said that is not pertinent to the case at hand.
I did not photograph the tires in the early days of my service to the shopping centers.
Now I am taking photos of the before and after of the marks on the cars tires.
But we are talking about thousands of cars at a time between two shopping centers.
It takes me six to ten hours to go through all the photos and delete the ones not towed and find the ones that were towed.

So I am looking for software that will sort out the photos of the cars plate number and only save those that have two photos of the same plate at two different times, and will show the date and time.
Can anyone help me with this to locate software of this type? If anyone knows of any shareware, or free ware it would be perfect. Thanks, Tow Joe