Here are some figures.
European Jewish population distribution, ca. 1933
Jews have lived in Europe for more than two thousand years. The American Jewish Yearbook placed the total Jewish population of Europe at about 9.5 million in 1933. This number represented more than 60 percent of the world's Jewish population, which was estimated at 15.3 million. Most European Jews resided in eastern Europe, with about 5 1/2 million Jews living in Poland and the Soviet Union. Before the Nazi takeover of power in 1933, Europe had a dynamic and highly developed Jewish culture. In little more than a decade, most of Europe would be conquered, occupied, or annexed by Nazi Germany and most European Jews—two out of every three—would be dead.
US Holocaust Memorial Museum
https://encyclopedia.ushmm.org/content/ ... by-countryThe figures are similar enough to what I've seen elsewhere to be taken as reliable and can be checked by various Censuses, give or take a couple of years and a few thousand in some of the larger populations. They also tally fairly well with the records made by the Nazis of from where the Camp victims were transported.
I'd be more wary of the USSR, I think that number may include the Jewish Autonomous Oblast, as well as Jews scattered throughout the rest of non-European USSR.
https://en.wikipedia.org/wiki/Jewish_Autonomous_Oblast