Consider the energy consumed by a 300 W
Light bulb in an hour.
How many flights of stairs would you have
To climb to equal the work of the lightbulb?

Depends on how many steps in a stairway. How many watts of energy are generated by climbing the stairs? Google that.

Work of the light bulb = power times time, and work against force of gravity = mgh. You haven't given the mass of the person climbing the stairs, so perhaps they want you to use an estimate for a "typical" person. With that you can find the value of 'h', and then to convert to flights of stairs you ned to estimate the height of a "typical" flight of stairs.