I was once at/in
我曾在搬家公司工作过溜进去偷出来的
I used to work for a moving company—I snuck in and stole it.
— 空之境界 第五章 矛盾螺旋 (2008)
我曾在罗马生活过。
I once lived in Rome.
我曾在英国留学英国淑女全要
I studied in the UK, where all the ladies are proper English ladies.
— 小姐 (2016)
我曾在一家饭店工作过。
I used to work at a restaurant.