This is the question: Did there use to be a different capital city? So, I don't know if I have to ask " Yes, it did" or " yes, There was"..I will be so thankful if you can help me! Thanks
It's common in immediate answers to questions during conversations, especially simple ones, to elide everything after the verb or first word of the verb, because the rest can be assumed from the question.
So you say:
There was (short for "There was a capital city.").
There did (short for "There did use to be a capital city." This is more emphasized than the above).
You wouldn't say Yes, it did because the there is the subject of the question, not it.