Difference between どこが and どこで in sentence


I was practicing some writing and attempted to write the following sentence

> Where can I find the cat food?

I originally wrote

> 僕は **どこが** 猫用の食べ物を見つけられますか。

However I was corrected to

> 僕は **どこで** 猫用の食べ物を見つけられますか。

What is the difference between the two sentences? Why is どこが wrong?




どこが is wrong (here) as the place is not the subject of that sentence. Imagine
to replace it with the position of the cat food: (wrong) 僕はトイレが猫用の食べ物を見つけられます.
Here you probably wouldn't even consider saying it in this way.

So the right thing to do is to use で for the place you do the action
(searching), therefore also for the question word that asks for this place.




The answer might be grammatical but it sounds slightly off, you want to say

Neko no esa wa doko ni arimasu ka.

The whole "where can I find" idiom doesn't make sense in Japanese.

