Can I get Pages for macOS 10.13.6?

Not from the Mac App Store which now requires the installation of macOS Catalina (10.15) or later before you can install Pages v10.3.5.

If you have never installed Pages, then the answer is no.

If you previously installed Pages v6 or later on macOS Sierra or earlier, then there is a slim chance you can get the App Store to upgrade it to v8.1, the last compatible version for macOS 10.13.6.

Launch the Mac App Store, and sign-in with the same Apple ID that you used to install Pages previously. Press the option key and select the Purchases tab. This will show your previous "purchases" and if the Pages application there shows an install/update button, click it. It will initially tell you that you cannot install Pages v10.3.5 as the requirements are not met, but it may then offer to update your currently installed Pages to its latest compatible version. Do that, if offered. Look for Pages v8.1 in your Applications folder.