how to get internal data from api?(react,node)

Question

I am using reactjs for frontend and nodejs for backeand and my database is mongo. My api is like this:

"data": {
    "role": 1,
    "students": [
        {
            "_id": "5c6f187aaaaafa2f0cbaaf12",
            "email": "s2@yahoo.com",
            "lastname": "abc",
            "firstname": "def"
        }

} How can I access the data inside the students field, for example the value of firstname??