3.5mm male to USB A female plug converter out of your iPhone or iPad
https://www.amazon.com/3-5mm-Audio-USB-Female-Converter/dp/B01CA5MDSY/ref=sr_1_3?s=electronics&i...
(find better quality if you can)
Use with a conventional USB A to B cable to the Modi.
Personally, I went to an Aries Mini. The wireless let me get rid of the long USB cable. The Aries is controlled by the DS Lightning app from the iPhone.