You have a misplaced closing brace }
The end of main() is missing its closing brace, instead it has ended up somehow right at the very end of the file.
Where you provide the definition of function FindCost(), remove the semicolon at the end of the line.
The variable named numPieces does not exist (but pieces does).
Your findcost function is being defined inside main. Don't do that.
double FindCost (char woodType,int pieces,int width,int length,int height); has a semi-colon on the end. It shouldn't be there when you're defining a function; only when declaring a function.
Your code outputs the total cost before you calculate it. That makes no sense.