converting enum switch from c++ to C

Question

How do I change this code from c++ to c if I can't use "::" to denote enum variables/elements? Also, I keep getting an "identifier 'GameState' is unidentifed" error message any time it's used outside the enum declaration that seems to be related to this problem somehow?

Header

void gameStateManager(); 
typedef enum GameState
    {
        MENU, PLAY, EXIT
    };

GameState gameState;

Source

void gameStateManager()
    {
        switch (gameState)
        {
            case GameState::MENU:
            //button press selections that lead to Menu
            break;

            case GameState::PLAY:
            //button press selections that lead to Play
            break;

            case GameState::EXIT:
            //button press selections that lead to Exit 
            SDL_QUIT;
            break;