Is there a button on statistics calculators that easily finds the range of the numbers? I am using window's pre-installed calculator.
Hmm I don't know of any hardware calculator which do so, since it is so trivial to calculate the range.
Basically the range is the maximum number minus the minimum number. In your example it is just $40.5-34.3=6.2$.
If you have many numbers, you can use spreadsheet if you like. In Excel it is just =MAX([cells]) - MIN([cells]).