Creating my first complex function

Hello, First of all I am sorry if this is a stupid question but since I am somewhat new to excel, I have no idea where to look to find answers since I am unfamiliar with proper terms for a google search but here is what I want to do:

I have a savings worksheet, in one column(let's say A) it lists the months, in the next column(let's say B) it lists the amount saved after "A" months. I want to have ONLY two other cells, one where I can type in a value for B (or a month number) and the other cell will have some sort of a function that looks at the number I type into the first cell and then display the corresponding value in column "A"

If I am still not making since:

A B
1 $1
2 $1.2
3 $1.21
4 $1.29
5 $1.30
...

Cell One: Type in month number
Cell Two: Automatically Displays corresponding cell in column B