Thank you for your post and welcome to the Bose Community.
The iPhone 8 does not feature a regular 3.5mm AUX port, therefore, in order to connect the QuietComfort 3 headphones, you will need an AUX to lightning adapter.
Let me know if you have any further questions.
Charlotte G - Community Support
Do you have the QC3 Bluetooth Communication Kit?
If so, you can pair your iPhone but only for taking calls. The QC3 Bluetooth Communication Kit does not support the A2DP Bluetooth profile for media playback.
If you do not have the Bluetooth kit, please let me know.