So if I'm using the area 8558.25 in that math I need to have it as 8558.25squared and then sqaure root it?

Volume in mm^3 = height in mm which is what the weather person reports times area in mm^2

and about your earlier question:

I've got the total volume/capacity that fell (3.51125KL) and the total area that it fell in (8558.25m).
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this is incorrect
the area must be in length squared, like m^2

By the way, convert the depth from mm into meters and do it in meters^3.

Also by the way
1000 liters = 1 m^3
so 1 kL = 1 m^3

rewriting what I guess you mean

I've got the total volume/capacity that fell (3.51125KL) and the total area that it fell in (8558.25m^2).

I say using approximate numbers:
volume = 3.5 kL = 3.5 m^3
area = 8500 m^2
then height = volume/area = 3.5 m^3/8500 m^2
= .0004 m = .4 mm

To clarify, if you have the area measurement 8558.25, you do not need to square it and then take the square root to find the original value.

The square of a number is the result of multiplying the number by itself, while the square root of a number produces the original value when multiplied by itself.

In mathematical terms, if you have a number x, squaring it is represented as x^2, and taking the square root of x^2 is represented as √(x^2) or |x|.

So, if you have the area value of 8558.25, you don't need to square it and then find the square root to obtain the original value. The value itself is the original area measurement.

However, if you have the side length (or any other dimension) of a square and you want to calculate its area, you would need to square that value. For example, if you have the side length as 92.5, the area can be calculated as 92.5^2 = 8556.25.