Question

when will you buy a new dress​

Answer 1

Answer:

Where did you bought’ is always wrong. The correct form is ‘where did you BUY’.

Since the questioner is asking about a SPECIFIC dress, you would need to use the article THE, not ‘A’, or use ‘that’ or some other word indicating a SPECIFIC dress:

‘Where did you buy THE dress’, or ‘Where did you buy THAT dress’

‘From’ is not necessary, but some people would add it in speech. However it is not really correct grammar to do so.

‘Where did you buy that dress?’ would be the most common, usual, and grammatical way to ask this question.