How to export all forms data at once?

I have 28 clone forms so how do I collect all forms data in single excel or csv file?????

If you want to export your forms data at once. You can do that by following this guide: https://www.jotform.com/help/374-How-to-Export-All-of-Your-Data-at-Once

I hope that helps. If you need further assistance, please let us know.