Where did you find it?
Yes, in such questions you should use the verb do. Note that after do you should use the bare form of the verb: find, not found. The verb do carries the Past Tense, being transformed into did, so there's no need for find to carry the Past Tense too. The two verbs work together, after all.
If you put this question into the Present Perfect, for example, you would need to use have:
Where have you found it?
Both do and have are "auxiliary verbs".
If you have a statement
I have found it! (Present Perfect)
..and you want to transform it into a question, then you have your auxiliary verb ready: it's have:
Where have you found it?
But if you have a statement
I found it! (Past Simple)
There's no auxiliary verb in it. But to pose a question you need an auxiliary verb! What to do? You have to use do. This is called "do-support":
Where did you find it?
So it all depends on whether there's an auxiliary verb of some kind in the statement you want to transform into a question. If there's no such verb, use do.
But there's an exception: in some questions, there's no need for an auxiliary verb:
- Who found it?
- How many people found it?
It's because the pronoun who serves as the subject of sentence 1, and the question words "how many" in sentence 2 refer to the subject of that sentence, which is people.
P.S. The clause
Where you found it.
Will not work as a question. It might be included into some sentence, like this:
Remember that golden coin? I visited the place where you found it, and found another.
There are two uses for using the past in your example
Did you know
Did you know that February has 29 days every four years?
Do you know that February has 29 days every four years?
The first question is more wondering if something is common knowledge for most people, the second is just a question to the person being spoken to.
P1: I didn't know how often the train comes by.
Did you know that the train comes by every hour on the hour?
P2: Why yes I did, it's in the schedule.
It is also used to shift the timeframe of the question to the past and is meant to gain the understanding or viewpoint of the questionee at that point in time
You brought an umbrella, did you know it was going to rain?
Did you know it was going to rain before you left home?
would be asked after it has started raining, since
You brought an umbrella, do you know if it is going to rain?
would not make any sense at that point.
Best Answer
You can use both the sentences. But the sentence (did you like it?) is appropriate grammatically. You can use the second one sentence in informal usage and you tone/accent should be like that you are asking a question.