네, 맞습니다. 여기서 then은 부사로, at the time 혹은 at the time in question을 의미합니다.
예: I didn't know what I wanted to study back then.
= I didn't know what I wanted to study at that time. (그땐 내가 뭘 공부하고 싶은지 몰랐어.)
예: I was visiting my parents then, and I heard about the incident on the news. (그때 부모님 댁에 있었는데 뉴스에서 그 사고를 봤어.)