Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Columbia, Missouri to Nashville as you normally would.
There are currently 3+ open flights from Columbia, Missouri to Nashville within the next 7 days for less than $600.
This is defined as Columbia Regional Airport (COU) and Nashville Intl Airport (BNA). Codes like Nashville Intl Airport are often used to just call airports uniquely.