/Utilities/Migration Assistant.app

The more efficient way of doing this is to Use Setup Assistant on first run, which is launched automatically when you specify that your files are in another attached location.
You can migrate files across your local Network, but it is very slow over Wi-Fi. You may need to enable
System Preferences > Sharing > File Sharing ...
... on the old Mac.
You can also migrate directly from your Time Machine backup drive.
¿Don't yet have a Time Machine Backup drive? Now is a really good time to make one for your old Mac, then "take it over" for use with your new Mac.
Back up your Mac with Time Machine - Apple Support
Any external drive will do in a pinch, but a drive 2.5x to 3x the size of what needs to be backed up will be trouble-free for a long time. The drive does not need to be fast.