To get the number of OHSAA recognized teams from last season, you would need to count the number of teams who had at least 7 wrestlers compete(wrestled in a match, look at bracket) at the Sectional Tournament in 2019.
I count 531ish (couple sectionals didn't have entry grids on baums so I estimated those).
187 D1
178 D2
166 D3
Of course there are more "teams" listed in D3 than D2 and D1 because there are far more teams with less than 7 in D3 than the others.