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The goal here is to be able to swim continuously for 15 minutes. If you are not comfortable with swimming I would suggest to hire an instructor. Focus on technique not speed.
The immediate goal is to master bike handling and to develop some muscles specific to cycling. Spin don't mash. As a beginner avoid heavy gears. Just try to spin with a comfortable load at 85 to 95 rpm. Be sure you practice hydrating while on a ride.
The goal is of course to run 7K without stopping but you can do run-walk strategy and it could be something like 6 minutes run followed by 1 minute walk then repeat until you reach the finish line.
Recovery days are important. Go to a spa.
Bike then quickly transition to run. Be sensitive to what your legs are feeling during the run. If something hurts remember that part of your leg then find 'muscle strengthening exercise' on the Internet specific to that part.
This session will give you confidence and something to expect when race day come. Don't go fast and hard just be quick with your transition.
You have 2 days of rest before the race and it will help your body to recover from the training that you did. Be sure to have plenty of sleep on Friday night if the race is on Sunday because you might not sleep properly on Saturday. Remember that the goal is to finish strong, not to win. Start from the back if you are not confident with your swim. Breathe properly. Be careful on the bike leg. Accidents happen. Don't over-bike. You know how long a 30K ride will take, be conservative and hydrate. On the run leg start with slow and short steps for the first 10 minutes then if you feel okay ... GO for it!