Sauce?
I did find some stuff myself, but there is discrepancy in the reports of the number of registered wi voters. Some places say 3.6 mil registered. I got about 3,289,000 total votes cast from realclearpolitics
https://www.realclearpolitics.com/elections/live_results/2020/state/wi/president/
https://worldpopulationreview.com/state-rankings/number-of-registered-voters-by-state