I work on the NASA NEO Surveyor project (and have helped out a lot on the WISE/NEOWISE mission, which found a lot of asteroids). I create and run simulations of asteroid detections, which ends up being mostly orbit calculations.
In the next few years the rate of detections of these sort of objects are going to go way up, NEO Surveyor and the Vera Rubin LSST telescopes are going to take our current knowledge of the solar system from about 1.4 million asteroids to approximately 10x that. It is somewhat difficult to estimate how many we will see, since the size distribution follows a power law, and small changes in our estimates of the slope can be huge changes the number which exist.
There are most likely hundreds of thousands to millions of a few meter sized asteroids flying around the inner solar system.
I did a large chunk of the numerical analysis in this paper: https://arxiv.org/pdf/2310.12918
I recommend figure 12 to get a sense of how far we can see at any given moment.
The definition which is commonly used as "hazardous" is about a 140m asteroid, which would cause a significantly bad day regionally, but not end civilization. That being said, 50m is still a very very bad day.
These meter-ish size ones usually just make a pretty fireball.
Some various links to data about this impact:
https://cneos.jpl.nasa.gov/sentry/details.html#?des=2024%20R...