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！
カナダ 
