The length of time that it takes for the average person to finish a 5k run is 25 minutes.
That is for the average well trained and fit 5 K runner.
If you're a beginner 5 K runner then it may take you 30 to 45 minutes to finish the 5 K run.
But once you get more fit and experience running in the 5 K race then you should be able to finish the 5 K run from start line to finish line in 25 to 30 minutes at most.
Make sure your health is up to the task and get some practice in and warm up your body before trying to do a 5 K race.