function multiplyOfThreeElementsQuantity(matrix) {
    var count = 0;
    for (var i = 0; i < matrix.length; i++) {
        for (var j = 0; j < matrix[0].length; j++) {
            count += matrix[i][j] % 3 === 0 ? 1 : 0;
        }
    }

    return count;
}

let matrix = [[1, 2, 3], [3, 4 ,6]];
console.log(multiplyOfThreeElementsQuantity(matrix));