Hard drive backup

Backing up a hard drive to a CD or DVD is not really a practical exercise. These discs have neither the capacity nor the speed for the job. Hard drives get backed up to another hard drive or solid state drives (SSD).

If you are wishing to backup the data on your own computer, please familiarize yourself with this: How to back up your Mac - Official Apple Support

The easiest and best way to back up your Mac is to use the Time Machine app (built into macOS) with an external hard drive. Back up your Mac with Time Machine - Apple Support

External hard drives are readily available through online purchase or at most office supply or local computer retailer at reasonable prices.

If you share what you hope to accomplish with us, someone here can provide great guidance for you.

There are also a couple of third-party backup utilities that many Mac users use:

Carbon Copy Cloner

https://bombich.com/

SuperDuper!

https://www.shirt-pocket.com/SuperDuper/SuperDuperDescription.html

In the old days, you could use one of these programs to make a bootable clone backup of your startup drive. (Time Machine backups are not bootable.) WIth all of the changes that Apple has made in recent years, it is becoming harder and harder to prepare and use a bootable external backup, but these tools are still popular.