week1:
3 x 4km runs/jogs at your own pace, i'd say 1km/6m30s as the minimum.
do one run every 2nd day
if you're sore, take it easy. first week is to get your legs back.
week2:
3 x 5km run/jogs at a higher pace, 1km/5m45s - 6m
week3:
1 x 5km run/jogs at 1km/5m30s
2 x interval training sets:
8 x 80m sprints with a 15s break between sprints, 2 sets, 3minute break between sets
2 x 800m runs in under 4m.
week4
1 x 6km run at 1km/5m30s MINIMUM
2 x interval training sets
could be a good place to start but up to you.
Good to get solid legs sure, likely a struggle to push all that through just for a sprint with his mates.
Stretch 3-5 times per day, run 3 sets of 3 x 50m sprints per day. You can get away without cardio for 50m sprints, it's all plyometrics and stored muscle energy based. Cardio doesn't kick in. At first don't sprint full speed and push for killer take offs, sort of ease your way in for the first week. Increase second week, balls out 3rd week and sustain 4th week.
Also get some good shoes while you train. You can practice your take off as well, get set, push off and get to a full sprint within as little number of steps as you can and then ease off and repeat 30 seconds later a few times in a row. Stretch before and after well. Walk before and after for warm up and cool down too.
Protip - stretch all morning before your race, also sneak in a quick 75% effort 50m sprint in secret about 5-10mins before you actually race. Get your muscles and heart rate ready to go from the start too.
Protip #2 - no alcohol for these weeks, drink heaps of water and don't eat big meals the night before or morning of the race. Have some pasta the night before, small meal and a banana for breakfast.