There's just no way to make any sort of semi-exact estimate of rapidly flying and darting insects on this epic a scale, but as dragonflies were everywhere I went on this property, and I saw hundreds and maybe a thousand+ in my very limited coverage, there were certainly thousands of dragonflies across the whole property, I'd say.
I've written about these swarms before, such as HERE, HERE, and HERE. Many people made comments on those posts, reporting additional swarms. If you saw such a swarm today or recently, or in the days to come, please leave a comment. Be sure to note at a bare minimum, the county, state if not Ohio, and a rough guess at how many dragonflies were present. If you know dragonfly identification and can say what species were involved, all the better.