You'll find the Date, Time, and Number formatting in windows under the "Regional" settings.

In the Search Bar, type "Region" and select "Region Settings".

On the Language & Region settings page, expand the "Regional Format" section by clicking the down arrow on the far right side of the "Regional Format" bar. Highlighted with the green arrow below.

Click on the "Change formats" button in the bottom right-hand corner of the window.

If the next set of windows shows enough selections to satisfy your needs, you can change the settings here.

If you still want to change more settings, like the number formatting, return to the "Language & region" settings page and select "Administrative language settings".

A new window will appear. You can change some of the settings from this page. There are still others available from the "Additional Settings..." button.

This is where you'll find the Number formatting tab.

Once the settings are configured as you desire, click OK to start closing the windows. Close all available windows and reboot your system.