You need some kind of DAC for the iLouds. There's one built into your PC that you can use, or you can get an external one.
The best value DACs if you don't need knobs, switches, multiple inputs, are dongles.
Apple A2049 ($9)
Ugreen 80583 ($40)
Moondrop Dawn 3.5 ($65)
I'd get the Ugreen and...