The number of meteors is almost impossible to estimate, as it depends on the sizes you are considering. Dinosaur killers only hit once every hundred million years or so, city-killers every hundred years or so. The wiki page about major impact events gives some estimated frequencies for large meteorites. The latest known ones were at Tunguska (1908) and Chelyabinsk (2013). More may have landed in the oceans. Fortunately, the Chelyabinsk meteor burned up high in the atmosphere; otherwise its effect might have been similar to Tunguska. At the other end of the scale, the number of micron-sized meteors is uncountable.
Scientists use automated camera networks to count the number of meteors and, by triangulation, to determine the direction each one came from. We know that some of them come in so-called meteor showers, which are associated with extinct comets.
It is easier to estimate the total amount of meteoric material that hits the earth and your quote of 100 tons/day is towards the lower end of the estimate range. 100 tons/day is 36,500 tons/year. Estimates vary widely and range from 15,000 to 70,000 tons/year. Another way of looking at these numbers is the estimate that roughly 100 meteorites heavier than 10 grams fall per million square kilometers per year, or one per year in an area the size of a small country. This is not something you'll notice readily, and is presumably one of the reasons why until about 1800 scientists believed that meteorites were earth rocks, not space rocks.
A steady 35,000 tons per year since the birth of earth would amount to about 1.5*10^14 kg which is insignificant compared to the total mass of the earth of 5.97*10^24 kg. I know that the bombardment was much heavier at the beginning - but then, as part of the bombardment the earth also lost an entire moon! Another way of looking at these numbers is the estimate that roughly 100 meteorites heavier than 10 grams fall per million square kilometers per year, or 1 per year in an area the size of a small country.