External drive for 24” M1 iMac

Yes, your Seagate Portable Drive with USB 3.0 should be compatible with your M1 iMac desktop. The M1 iMac supports USB 3.0 connectivity, so you should have no problems connecting and using your old drive. However, keep in mind that after being unused for a few years, it's always a good idea to check the health of the drive and backup any important data before relying on it for storage. If you prefer a newer external drive, you can consider that as well for better performance and reliability.

Yes the Seagate should work with your 24” iMac.

However, you may need a USB-C to USB-A adapter if the iMac only has two USB-C/Thunderbolt ports.

Plus depending on what you want to do with the Seagate drive?

You can most likely use it as is for sharing files between computers.

It will need to be reformatted for use as a Time Machine backup, which will erase any existing files currently in the drive.

den.thed wrote:

However, you may need a USB-C to USB-A adapter if the iMac only has two USB-C/Thunderbolt ports.

I believe that even if the OP sprung for the version of the iMac with two additional USB ports, those ports will be USB-C (USB) ports. Some sort of adapter may still be in order.

A lot of portable USB 3.0 hard drives have a USB 3.0 Micro B socket on the drive itself, so one of the options may be to substitute a USB-C to USB 3.0 Micro B cable for the USB-A to USB 3.0 Micro B cable that would have come bundled with the drive. E.g.,

https://www.amazon.com/Cable-Matters-Type-C-Micro-USB-C/dp/B00UUBQ710?th=1