Beginner to Mathematica's question using Module

[psb01080]

Okay, this is the question that i need to solve using mathematica:

Define the function f(n) which counts the number of zeros in n if n is the integer greater than 0.
If you input 105, 1005, 10005, find f(n).


I want to use Module in this question and I just found out that i have to use "Mod", "Count" and "Floor" but still haven't figured out this. Please help!

 

[CompuChip]

Of course, IntegerDigits and Count would solve the question right away, but I suppose that's no fun

Anyway, I suggest first trying to write down a general algorithm, then programming it in a Mathematica notebook, and only in the final step putting it all in one module. For example, how would you use the functions you quoted to get the i-th digit?