Militia Mile
After starting the mission, you can drive to the north to ambush them there. The convoy's not using durable vehicles and the escorts are not that heavily armed so it's possible to kill them quickly without any problems.
The Quick Fix
The convoy's projected path isn't far from where you accepted the mission. You can ambush them or just drive towards them and engage them directly. The convoy's not using durable vehicles and the escorts are not that heavily armed so it's possible to kill them quickly without any problems.