All that long explanation says is that she travels 3,333 miles at a rate of 41 miles per day. Put this information on a graph.
Before you can successfully start a graph, you need to guess how to divide up the units on each axis.
If the x axis is time (which is always is) and the units are days, you have to estimate how many days to show on there. (That's what they call estimating the domain). On the Y axis is distance. Not too hard to estimate that because when she's rowed 3,333 miles, she'll hit land. She' probably stop at that point.
Now, just plot points using the formula given. After one day, 41 miles; two days 82 miles, etc.