。
She bought a vacuum cleaner at the supermarket.
Literal
She [topic-は] supermarket [at-で] vacuum-cleaner [object-を] bought.
Clean structure: で marks the location of the action (where the buying took place), を the object purchased. 掃除機 ('vacuum cleaner') is a transparent compound: 掃除 ('cleaning') + 機 ('machine'). The 機 suffix is productive in naming devices: 洗濯機 ('washing machine'), 自動販売機 ('vending machine'), 飛行機 ('airplane'). スーパー is the standard short form of スーパーマーケット — the long form is rare in everyday speech.