Where are the USB Ports on my new M4 iMac?

Those 4 ports on the M4 iMac support both Thunderbolt and USB devices.

You can use USB-C to USB-A adapters.

for some examples:

USB-C to USB Adapter - Apple

https://www.amazon.com/dp/B07PDLQ555/ref=sspa_dk_detail_0?

https://www.amazon.com/dp/B08Z768LCW/ref=sspa_dk_detail_1?

https://www.target.com/p/philips-usb-c-to-3-0-usb-a-female-adapter/-/A-79804275

Or optionally get and use a USB-C Hub with USB-A ports.

For some examples:

https://www.amazon.com/s?k=usb-c+to+usb-a+hub&ref=nb_sb_noss

Each of the Thunderbolt ports can be used for USB-C devices as is. If you have any regular USB ones, you'll need an adapter.

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All of those ports are USB ports that can carry USB 2/3 signals (among other types of signals). They just aren’t USB-A ports. There are lots of ways to go between USB-C and USB-A in either direction when it comes to USB 2/3. But there are other things that USB-C can do, that USB-A can’t.

This is why the USB4 standard calls for USB4 host ports like the ones on your Mac to have USB-C connectors.

If you get a USB hub make sure you get a self powered one. That way you won't overload the capacity of the port it's plugged into.