Insert string behind consecutive numbers in string?

I'm building a calculator using eval() and need exponents from "^".

I want to take

1+2^

and replace "^" with ","
and insert "Mathf.Pow(" behind "2".
I need it to work even when "2" has more than one digit.
It needs to become

1+Mathf.Pow(2,
Now, when user types "3", it becomes

1+Mathf.Pow(2,3

I already know how to add ")" when user types a non-number.
I will then eval() the expression and return the answer.

Thanks for the help! :)