Simplify the following text for a Grade 5 native English-speaking person.
Original: Lower Silesia and most of Upper Silesia became part of the Kingdom of Prussia in 1742 during the First Silesian War . A small part remained within the Habsburg-ruled Bohemian Crown as the Duchy of Upper and Lower Silesia , colloquially called Austrian Silesia .
Simplified: It can be found in the south Poland and in east Silesia ( called Upper Silesia ) .