Mac mini M1 use 2 monitors not split, how to do like image attached on Mac Mini M1

I can't show my arrangement as it's not currently set up.

But I found a link to the Apple Support that describes the process.

You need to set extended desktop and then arrange the screens.

Use multiple displays with your Mac - Apple Support:

https://support.apple.com/guide/mac-help/use-multiple-displays-mchl7c7ebe08/mac

Set up the displays as an extended desktop

You can arrange your displays in any configuration to create an extended desktop. For example, you can set your displays side by side to create one large continuous desktop.

1. On your Mac, choose Apple menu  > System Preferences, click Displays, then click Arrangement.
2. Follow the onscreen instructions.

Once you have the desktop extended and arranged, you will need to resize the application windows to extend across the desktop from one monitor to the other. Application windows are resized by clicking and dragging the edge of the window. (You'll see the mouse pointer change to a two-way-arrow <–> at the drag point.)

For example, if you have a video playing on the left monitor, click-n-drag the right edge of that video window to the right and past the right edge of that monitor and into the display space at the left side of the monitor on the right.

Continue dragging until that video application window fills the width of both monitors.

Do the same for any application window that you wish to fill both monitors.

NOTE- the windows of some applications may not take kindly to this extreme resizing and may look not-so-great.

Another thing that you might want to do, is go to Mission Control and uncheck the boxes.

Configure the displays as Extended Desktop, not mirrored.

System Preferences > Displays.