My consumer math assignment says : " Mr. Johnson found on the internet that his car had a ‘trade-in value’ of $4295 but a ‘retail value of $9110. Check the internet and find out what these values mean and why such a difference exists." But I have looked for that and all I can find is the trade in values for specific cars…please help me?

The trade in value is how much dealers will typically buy your car from you for when you buy a new one.
Retail value is what a dealer typically sells it for.

In your situation, The dealership would buy Mr. Johnson’s car from him for $4295, then they would sell it to someone else for $9110, making a profit of $4815