Assuming that the units of speed are also in minutes, for instance km/min or m/minute. Then you would not need to convert time into another unit. As for multiplying the bases of 10, remember that 10 = 10^1. So it would be 10^8+1 = 10^9. So the result would be 24 • 10^9 but in proper scientific notation it would be 2.4 • 10^10.
Yet, I believe you are working with the speed of light and thus you would need to convert 8 minutes into seconds which would be 8 • 60 = 480 seconds. Then do the following operation:
480 = 4.80 X 10^2
(4.80 X 10^2 seconds)(3.00 X 10^8 metres/second)
Simply multiply the whole numbers, and the bases of 10, and put in proper scientific notation.