When I started reading, I didn't know where to take a break in each of the sentences.
I wasn't sure where to pause when I first started reading.
ーWhen I started reading, I didn't know where to take a break in each of the sentences.
「読み始め、それぞれの文をどこで区切れば良いかわからなかった」
to take a break を使って「区切る」を表現できます。
ーI wasn't sure where to pause when I first started reading.
「読み始めに、どこで区切るかわからなかった」
to pause を使っても「区切る」を表現できます。
ご参考まで！
I couldn't immediately tell where the sentences were supposed to break.
「どこで区切って読めばよいか、すぐにわからなかった」は英語で "I couldn't immediately tell where the sentences were supposed to break." と言います。
"I couldn't immediately tell" は「すぐにわからなかった」を表し、"where the sentences were supposed to break" で「英文がどこで区切られるべきか」を表現しています。
カナダ 
アメリカ合衆国 
