"This model has usb-c. Won’t connect to thunderbolt?"
I believe the 2017 iMac has BOTH USBa -and- USBc ports on the back.
They ARE NOT "thunderbolt" ports (strictly speaking), although they DO support thunderbolt3.
They ARE called "USBc ports". You should learn to refer to them that way, it avoids confusion.
They support:
- USBc
- Thunderbolt3
- Display output
Again, you have a USB interface.
You DO NOT HAVE a "thunderbolt" interface.
It can plug into the USBa ports.
I believe itt should also be able to plug into the USBc ports using the proper cable. Consult the documentation that comes with it.
However, I'd use the USBa ports, that's "all it needs".