The short answer is: about one thousand years. See the attached Related Link.
Since about AD1100.
Most jews lived in Nove Mesto
The current Jewish population of Poland is about 8,000 only. See the Wikipedia article on The Jews in Poland. (Compare with an estimated 3.3 million in 1939). In 2010 3,200 Jews lived in Poland according to http://www.jewishvirtuallibrary.org/jsource/Judaism/jewpop.HTML.
In Poland, because is where large numbers of Jews lived.
1,000 years.
Jews were distributed all over all of Europe, but the largest concentration lived in Poland and western Russia.
They were turned over to the Nazis and killed or put in concentration camps
Since the Middle Ages, at least.
The place where the Jews lived in Poland (and other countries like Russia) was called a GHETTO. Each ghetto had a name too. Watch the move Defiance if you want to get a good idea about ghettos.
They killed all the jews and Poland had lots of jews.
There are about 8,000 practising Jews in Poland. In 1939 there were about 3.3 million ...
Jews have lived in the area (Bohemia, Moravia, Slovakia) since the Middle Ages, though there were periodic expulsions and readmissions.