10^6 or 10⁶ is the number 1000000 (one million).
m^3 or m³ usually means cubic metres and is just a measure of volume, just like m means metre, a unit of length, or m^2 or m² usually means square metre, a measure of area.
On your Casio calculator, there may be a button marked ×10ˣ, so if you press 1 then the button then 6, the calculator will give you 1000000. 10^6 is just a shorthand way of writing a million without having to write all the zeroes. So 10^25, say, is much better than writing 1 followed by 25 zeroes, and enables calculators to handle very large (or very small) numbers (10^-6 means a millionth).
