Where is the position of shadow in the mid day?

One definition of midday is halfway from sunrise to sunset. If the Earth only rotated on its axis, this would be when the Sun is at its highest point. Another definition of midday is when the Sun is at its highest point. Between the Tropic of Cancer and the Arctic Circle, the Sun is due South, so the shadow is due North. This is probably all the answer you need, but there is more.

Because the Earth also orbits around the Sun, the exact moment of midday can be a little different between the two definitions, but they're close.

Between the Tropic of Capricorn and the Antarctic Circle, the sun is due North, so the shadow is due South. Between the Tropic of Cancer and Tropic of Capricorn, the Sun is either due North or due South or directly overhead, depending on the time of year.

North of the Tropic of Cancer, a single day or single night can be longer than 24 hours. Theoretically, if the Sun rises in March and sets in September, midday is in June, but it's not really very meaningful. Similar logic applies South of the Tropic of Capricorn. At the North or South pole, the Sun just circles around the sky for weeks, so the shadow can be any direction.

Notice that midday is not necessarily 12:00. It's usually close, but can be an hour or more different due to standard time zones. The fact that the Earth's orbit is not circular also adds and subtracts a few minutes depending on time of year.