converter.js

var fs = require('fs'),
    Converter = require('swagger2-postman2-converter');

function handleConversion(originalFileName, newFileName) {

    // read the local swagger file
    var swaggerObject = JSON.parse(
        fs.readFileSync(originalFileName, 'utf8')
    );

    // convert Swagger 2.0 to Postman 2.0
    var conversionResult = Converter.convert(swaggerObject);

    // create a new local file in Postman v2.0 format
    fs.writeFileSync(newFileName, JSON.stringify(conversionResult.collection, null, 2));
    console.log('Converted ' + originalFileName + ' to ' + newFileName);

}

handleConversion();

It requires arguments passed to the script.
Change the last line to handleConversion(process.argv[2], process.argv[3]); (these would be not system arguments you pass)
and call it like `node converter.js "path from" "new file name"