Translation:There are hundreds of lamps in the shop.
can I also say something like "Det finns hundrar lampor i affären"? so what's the special context of using "hundratal"?
If you say Det finns hundra lampor i affären, you're saying that there are 100 lamps in the shop, and people will wonder how you counted them. hundratals means 'hundreds of', it could be anywhere between 200-900 maybe, you don't know exactly.
I’d say butik is typically a small store that usually specialises in one thing whereas affär is more general and is also used for bigger stores and stores that sell various things etc.
You could, but I think affär is also more general and can be used to cover a lot of butik-senses. But in this case, I imagine the store is quite big and professional since we’re using affär whereas a butik would more be like ”that small lamp-show down the corner”.