Where do meteor showers occur mostly?

Answer 1

It's less of of a "where" and more of a "when". There are meteor showers through the year and you stand a good chance of seeing them, providing it is clear, dark and, ideally, a new moon. The most famous are probably the Perseids which occur in mid-August.

Answer 2

Specks of dust and sand from space enter earth's atmosphere and burn up.

These specks of dust and sand generally came from the tails of comets and thus the earth encounters them periodically as it crosses the orbit of the comet that ejected them.
As the Earth makes its orbit around the sun, at various times it passes through dirtier parts of space. Normally it is because Earth is passing through the remnants of a tail of a comet. As we pass through that part of space, some of the dust and dirt gets into our atmosphere and it burns up and we see a meteor. You could see a meteor on any night of the year, as there is always dirt in space, but during a meteor shower such as the Leonids, or Perseids or Orionids and others, there is an increased amount, so the likelihood of seeing meteors increases. As our orbit of the sun takes the same path around the sun each year, we pass through these dirtier areas at the same time every year, which is how we know when a meteor shower occurs. There are many showers during the year but some of the best ones are the Quadrantids in early January, the Lyrids in late April, the Perseids in mid-August, the the Orionids in much of October, the Leonids in mid November and the Geminids in mid December.

All the showers get their names from the constellations visible in the part of the sky from where the meteors seem to come from, although there is no connection between the constellation and the meteor shower. So for example, the Perseids seem to come from the area where Perseus is and the Leonids seem to come from the area where Leo is.