backup

I recommend using a SanDisk Professional G-DRIVE - Western Digital as your backup drive. You can then follow the Apple Support steps to setup your Time Machine backup: Back up your Mac with Time Machine - Apple Support.

I personally also use iCloud in addition to Time Machine to sync all my files and photos to all my Apple devices. Although iCloud is not a "true" backup service, iCloud can also act as an emergency backup, but this is why iCloud should be used in addition to Time Machine. I strongly recommend using it. Here are some resources on setting up iCloud for Mac:

• Upgrade to iCloud+ - Apple Support
• Set up iCloud Drive - Apple Support
• Add your Desktop and Documents files to iCloud Drive - Apple Support

Jack

Most external drives will require reformatting.

https://support.apple.com/guide/disk-utility/erase-and-reformat-a-storage-device-dskutl14079/mac

While it may not be as robust as some other external drives, the Seagate is better than nothing and will work just fine.

All disks/storage devices, solid state and hard spinning disk type, require formatting. Many come with Windows formatting and must be reformatted in an Apple format. You can't get around this requirement.

Some Flash drives, and others too maybe, come in exFAT or MSDOS FAT which can be used "as-is" but they are generally not suitable for backing up. For local backing up you need either a Solid State Drive (SSD) or a hard disk drive (HDD).