Here's what I get when I want to check my operating system build:

Using the Settings App:
Press Windows + I to open Settings.
Go to System > About.
Here, you'll see information about your device, including the edition and version of Windows.

Using the Run Command:
Press Windows + R to open the Run dialog.
Type winver and press Enter.
A window will pop up showing your Windows version and build number.

The new Settings app also offers build, edition, and version information in a user-friendly form. Hit Windows+i to open Settings. In the Settings window, navigate to System > About. Scroll down a bit and you'll see the information you're after.

Unfortunately Microsoft doesn't provide a mechanism to determine the cumulative update version. Since they don't really provide operating system service packs any longer, it would be useful information.

In the Settings window, go to “System” and then select “Display” from the left-hand menu.

Under the “Scale and layout” section, you will see a dropdown menu labeled “Change the size of text, apps, and other items.”

Select a higher percentage from the dropdown menu (e.g., 125%, 150%, 175%) to increase the overall size of text and other items on your screen.

In the Run window, type winver and click OK.
The window that opens will display the Windows 10 build that is installed.