Adding a semicolon to a function definition turns it into a forward declaration - which can't have a body.
Remove the semicolon at the end of the "main" line.
is a function: you need to call it by appending open and close round brackets to the name:
int x = foo();
Or if you need to supply parameters, they go inside the brackets:
int x = foo(666, "a parameter");
requires at least two parameters (a format string, and one or more pointers to locations to store the information) so they go inside the brackets:
int r = scanf("%d-%d-%d", &x, &y, &z);
You will need to do the same thing with