There are a few that come pre-formatted for Mac as HFS+, but finding them is not always straightforward.
For example: https://www.seagate.com/manuals/backupplushub/optional-formatting-partitioning/
However I've only ever seen the Windows formatted version.
There are others that claim to be Mac formatted directly but its hard to be 100% certain. For instance: https://www.amazon.com/Fantom-GF5000QU3-External-Firewire-Aluminum/dp/B00YUU3XJG?th=1
Reviews and questions claim some were already formatted as HFS+ out of the box, other say it came as NTFS for Windows. So you take your chances.
Formatting is not difficult though. Its juts a matter of opening Disk Utility, selecting the drive, setting the format (HSF+ or APFS), and hitting the format button.