Translation:These are bought at the shopping mall.
Thank you! I didn't understand the use of the word "bought" and also assumed it was past tense. I speak English well BUT was never very good at all of the grammar rules. So, while attempting to learn a new language, I am beginning to understand how little I understand about my own language. OY VEY!!!
The difference between "ci" and "si" has nothing to do with the difference between singular and plural. "SI" is the right pronoun here because it's the third person reflexive pronoun. Si lava = He washes himself; si lavano = they wash themselves; but ci laviamo = we wash ourselves. The reflexive form is also used to form the passive: Si lava = he is washed; si lavano = they are washed. The passive is what you have here.
Google translate tests: the English of what DL want (these are bought at...) gives "questi sono acquistati presso il centro commerciale". Totally different!! Pop in the italian DL uses here (questi si comprano al...) and, sure enough, we get back to DL's English. I'm guessing an Italian speaker would be able to advise..? Please!!