It appears you have all the information, it's just that you don't understand how to interpret it.
If you are maintaining a checkbook, which it appears you are, and as you should, then each check entry should have a description; car purchase, car sale, expense, etc.
Based on the limited information, you appear to be able to determine sales, purchases, etc.
You would certainly benefit from meeting with a tax professional, or at a minimum, a bookkeeper who can pull together the information in your checkbook.
As noted by @Mike9241 , if you can't figure out what is in the checkbook, then you certainly aren't going to be able to challenge any potential IRS audit. That is not a good end result.
*A reminder that posts in a forum such as this do not constitute tax advice.
Also keep in mind the date of replies, as tax law changes.
