Urgent!

Can I please get help on this last program on C++ I dont know what to do.

Define a function GetLength() that takes one integer parameter passed by reference as totalMeters and two integer parameters as kilometers and meters. If both kilometers and meters are non-negative, the function computes totalMeters and returns true. Otherwise, the function returns false without updating totalMeters. Ex: If input is 302, then output is: Invalid. Total meters: Notes: - totalMeters is computed as (kilometers * 1000) + meters. - A non-negative number is greater than or equal to 0