Exporting your Hello Epics data
Exporting Parent/Child Links
Hello Epics uses attachments to store parent/child relationships. Those attachments are located on the parent card, so in order to tell a card's parent, you'd need to look at all of the attachments of all cards and find attachments that link to the card.
The attachments are in the format of: https://trello.com/c/{cardId} where {cardId} is the long id of a card (e.g. 5b0dfa61003d9db2aab6f895).
You can find a list of attachments for a parent card by using Trello's CSV or JSON export feature or by using Trello's API.
Finding the Name of the Parent Card
As described above, the attachments are urls, the last part of which matches the Card ID column of Trello's export.
If you are using Excel you can follow these steps to add the Parent Name as a column in your export:
1) Insert a new column after "Card Name" and call it "Parent Name"
2) Use this formula in the column: =IFERROR(INDEX(B:B,MATCH(TRUE,INDEX(ISNUMBER(SEARCH("*"&A2&"*",J:J)),,),0)),"")
Note that this will only work if your cards have a single parent. If you have multiple parents only the first will be shown.