How do I update my MacBook Pro to macOS High Sierra 10.13.6

Hello, Angela.

Start here to make sure that your MacBook Pro meets the system requirements for upgrade to High Sierra:

MacOS High Sierra - Technical Specifications

If your MacBook Pro meets system requirements for High Sierra, then make sure you have a current and viable backup of your data using Time Machine or other backup software.

Back up your Mac with Time Machine - Apple Support

Make sure your MacBook Pro has the latest updates for your current OS 10.12. Click (Apple menu) > About This Mac > Software Update...

Now, using the Safari browser (others may not work), you can download the High Sierra installer from the App Store.:

Download macOS High Sierra from the Mac App Store

When the installer has finished downloading, double-click it to begin the upgrade process.

If all goes well, you should be running macOS 10.13 High Sierra when the process completes.