Hi Robert,
It depends.
If you want to start a brand new set of backups for your new Mac, you should either use a new external drive (if you want to preserve the backups for your previous Mac) or erase the drive in Disk Utility, if you are fine with deleting your previous backups. Then, set up the drive in Time Machine preferences.
If you want to import the contents of the last backup onto your new Mac, and then continue the backup history, see below:
If your previous Mac was last running macOS Catalina or earlier, you might want to consider importing the contents of your backup onto your new Mac (use Migration Assistant), and then erase the backup drive and start over with Time Machine. This is because macOS Big Sur and later support the APFS format for Time Machine, which allows backups to complete faster.
If you don't want to erase your backup drive, you can continue backing up with your existing backup history on your new Mac, after you import the contents of the last backup onto your new Mac. You might be asked to inherit the backups after the import is complete.