Hey alexpfi1,
Thanks for your post!
Welcome to the IK forums.
The sound you are hearing can be resolved by connecting your UNO Synth to a different power source like 2X AA batteries, a USB battery pack, or a 'wall wart' (Mobile device charging block).
If this is not an option, a good solution would be to 'clean' the signal coming out of your 3.5mm port going into your audio interface. Check out the audio conditioner below. This is an inexpensive solution which will help you with your particular set up. Connect this between your UNO Synth and audio interface.
https://www.amazon.com/Mpow-Ground-Isol ... onditionerAs for the cable to connect to your Audio Interface. Yes, a 1/4" to 3.5mm cable would work for this connection. Unfortunately, I don't believe the Hosa cable you sent over will 'clean' your signal in anyway, but Hosa is a great brand and their cable should work with the above solution.