Preview on device

In addition to what @Jon Fritz tells you, you can also edit the list of your browsers and from the console (F12) of any modern browser, you can access a simulation of different mobile devices.

As @Jon Fritz said, Device Preview is gone.

Upload your work to a test folder on your remote server.  

Test your site's performance from all major devices & browsers. 

The best option for previewing your work across multiple devices on your network would be to set up a local testing server like the free XAMPP.

Once you've placed your site's root folder within the testing server htdocs folder, you run XAMPP as Administrator.

From there, you can use your local network IP address followed by your site root folder (example: 123.45.6.7/MySite) in your browser's location bar to view your work on any device connected to your network.

The Preview on Device functionality was removed from DW by Adobe in November of 2021...

https://helpx.adobe.com/dreamweaver/using/device-preview-troubleshooting.html#:~:text=Effective%20from%20November%2016%2C%202021,Device%20Preview%20on%20your%20devices.