I want to install gulp, for that, I saw this doc: https://preview.keenthemes.com/html/metronic/docs/getting-started/build/gulp, but I can't find a directory /theme/tools/
If you downloaded the Metronic theme demo from our website, you should find a "tools" folder in the root directory. Inside that folder, you can find the "package.json" file, which contains the dependencies required for the Gulp build system.