I'd want to pass the body parameters indicated in the screenshot.

I am using axios in my nodejs/express project . My request format is as shown below:
var config = {
    headers: {
        'Content-Length': 0,
        'Content-Type': 'text/plain'
    }
};
const testInput = (req, res) => {
    axios.post('https://api.sandbox.xyz.com/v1/order/new', { firstName: 'Marlon' }, config)
        .then(function(response) {
            console.log('saved successfully')
        })
        .catch(function(error) {
            console.log(error);
        });
};
How can I adequately pass the body parameters in this case?