how do i backup new macbook pro

I use CarbonCopyCloner (bombich.com, $40) which duplicates the format/contents of your internal. The clone can be used to option-boot (hold option key at boot time with external attached) in case of internal drive failure. The first clone takes long, subsequent backups will only move changed/new files to external and will archive old copies of the changed files on the clone.

Clones allow overwrite of the internal drive in case of system failure to get you back to where you were ... the newer systems will likely be just full-replace if there are issues because all parts are soldered to the logicboard.

Use Time Machine, and an external SSD or HDD, at least 2 times the size of your internal drive (recommended), or use a third party [well-regarded] tool called Carbon Copy Cloner, that let’s you create bootable backups.

Set up Time Machine, or use a tool such as the Disk Utility's Image or Restore functions, or drag-copy files to an external drive.

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Small caution on the "2x the size" rule. I have a 4TB internal drive, but do not back up to 8 TB disk. If you only plan to use 1 TB of a 4 TB drive, use a 2 TB backup. By the time you use 2 or 4 TB on internal and need bigger backup, you will have gotten good use of the 2 TB backup.