Well you did not show the figure, but I can show you how to do it.
Suppose the person is 6 feet tall and the bacteria cell is 1 micrometer in length.
So, put both magnitudes in the same units. I will use meter.
Person: 6 feet * 0.3048 m / foot = 1.8288 m, which in orders of magnitud is about 2 m
Bacteria cell: 1 micrometer * 1 m / 1,000,000 micrometer = 1 * 10 ^ -6 m.
Now divide: 2m / 10^ -6 m = 2,000,000
So a person is about 2 million times larger than a bacteria cell.
If the numbers in your figure are different you can use the same method to get a new result according to your figure.