In your project’s package.json you have this line:
This is probably what requires node-sass somewhere, change it to version 1.3.12 (the newest version of 1.x of this). Then run npm install.
The reason why this happens is complicated: node-sass on Windows has to download a compiled version that matches your node/npm. These are only available after the node/npm combination was released - duh. The app-scripts 1.3.7 version of node-sass was released before your node/npm combination. This causes the file not to exist, giving you this nice error message.