I'm being a bit (very?) anal here, but it's a 10k not a marathon nor is it a quarter marathon.
In any case, a week is a very short time to get ready!
You need to start running outside on the real road or trails. This is because treadmills don't work on all the same muscles as the real road. The machine maintains in a way pushes you at all times so you can push off the belt and there is a "give" vs on the road where the ground does not "give" on every step. As well the machine maintains a constant mechanical pace vs road running where you need to mentally maintain it.
You may notice this the first time you run and feel gassed and a bit achy in certain parts of your legs. So, start off easy because you may not be able to hit the same pace as on the treadmill, at least initially.
Overdoing it so soon could make you hurt too much on the actual run day.
Another piece is the fact that you have never run a continuous 10k. This means pacing is going to be very different. You cannot run 10k at the same pace as a 5k as you will wear down very quickly. Example if you do 5k in 30 minutes, you won't likely do 10k in 1 hour. Pace yourself to take longer, perhaps 1:15 to 1:30. Further in as you go through the run you can mentally reevaluate your condition and adjust your speed. It's better in this reduced training time to save a little gas for later.
One more thing is psychology/discipline. These runs have a lot of people usually, so keeping your pace and focus is very important. Don't get psyched into trying to catch up to someone running faster than you as they could have a different game plan and conditioning. Plan and keep a straight course to minimize waste of energy trying to dodge people and any obstacles