"How to migrate from M1 Mac Mini to M4 Mac Mini (one monitor, keyboard + mouse): How can i migrate from my old M1 Mac Mini to my new M4 Mac Mini using only 1 monitor, 1 keyboard and 1 mouse The M1 timemachine is a SSD. I use a 3rd party wireless keyboard and 3rd party wireless mouse however if I need to dig out my apple keyboard and mouse to make the migration easier, I will."
-------
Backup the New Mac, Once Complete:
Once the Migration has completed, check for updates. Keep restarting, until all updates have completed. Once complete, back up the new Mac with its own external hard drive.
Looking to Rid of your Older Mac?
If so, you should do so promptly. Perform as instructed here, including the TMB creation and iCloud logout: What to do Before you Sell, Give Away, Trade in, or recycle your Mac - Apple Support