On the Natchez Trace Parkway itself, the Jackson access point is mile marker 102; from there, you will drive north to the Tupelo Visitor Center (mile marker 266) and then leave the Parkway to head north on US-45 to Corinth. So mileage on the Parkway will be 164 miles, plus an additional 45 miles to Corinth. Enjoy your trip. Dogwoods should be out soon in this part of the world!