If you don't have wifi, what cable do you use to transfer files from an old iMac to an M1 iMac?

The fastest, most reliable and easiest method is described in Setup Assistant and Migration Assistant. Please never use Wi-Fi to migrate, this fails about 99% of the time!

Best way, is to connect the old iMac’s Time Machine back drive to the new iMac and migrate from it during the initial setup.

If the Time Machine backup drive has a USB-A cable, then you will also need a USB-C to USB-A adapter.

You’re welcome.

Your welcome, the migration should go very smoothly.