Complex sentence: Many older girls, with Hitler Youth were sent to Poland as part of the Germanisation efforts, to educate ethnic Germans, either living in Poland or resettled there from the Baltic states, according to German ways, and to organize the younger ones into the League.
Split into simpler sentences: Many older girls, with Hitler Youth were sent to Poland as part of the Germanisation efforts. Their task were then to educate ethnic Germans, either living in Poland or resettled there from the Baltic states, according to German ways, and to organize the younger ones into the League.