"There are pictures on the fridges, in which there are many apples."
Translation:Azokon a hűtőszekrényeken vannak képek, amelyikekben sok alma van.
I am always a little confused about word order when you have van/vannak. For example, here we have pictures on the fridge and apples in the fridge. For pictures on the fridge, vannak comes before képek in the duolingo translation (copied below). However, for the apples, van comes after the alma. Is there a rule that tells me where to place van/vannak?
DL Translation: Azokon a hűtőszekrényeken vannak képek, amelyikekben sok alma van
There is no rule to tell you where to place "van/vannak". That would be like the cart pulling the horses. The rule is about what to place before the verb! The place in front of the verb is the most emphasized place. So, you place in front of the verb what you want to emphasize. In the first clause: those fridges. In the second clause, the apples. These represent the most important information in the sentence.
In English sentences, the relative clauses usually follow right after the item they are referring to. So here it's likely the fridge that contains apples, unless you put some emphasis on the pictures.
There are pictures, in which there are many apples, on the fridges.
Or maybe even:
On the fridges there are pictures in which there are many apples.
A hűtőkön vannak képek, amelyeken sok alma van.