Heard on a WW II documentary the other night that pre-war Germany had an estimated 500,000 Jews. (Apocalypse WW II or one of those shows). Half fled pre war according to that source. Some to US, some to UK, some to France. Ones that went to France were rounded up after German occupation. French were not shy about turning them in. Poland had 3 million. USSR 2.5 million.

I found this:

https://www.jewishvirtuallibrary.org/jewish-population-of-europe-before-the-holocaust-map