I (hypothetically) looked in a book of statistics which says that there is a 3% chance of getting in an auto accident per kilometer travelled. What is the formula for determining the chance of getting home safe given the number of kilometers you have to travel?
Assuming independence of accident risk per km travelled, the probability of being accident-free for any one stretch of $1$ km is $1 - 0.03 = 0.97$.
The probability of being accident-free for $n$ such stretches is $0.97^n$.
That's what you've been asked to find. You can convert that to a percentage by multiplying by $100$.
If instead, you're asked about the probability of being involved in an accident over $n$ km, then this is $1-0.97^n$.
There are some big assumptions here: independence and even that you can divide distances in this sort of discrete fashion into $n$ "steps" meaningfully.