How to create dynamic database in mongodb?

I'm learning MERN stack development, when I tried to connect the database through .env file, everything was working fine. Here is how my database string looks like:

MYDATABASE_String="mongodb+srv://avnish:[email protected]/registeredUsers?retryWrites=true&w=majority"

It is working fine when I'm trying to register users, they go under registeredUsers. But now, I'm also implementing blog portion, so when I publish a new blog, it goes under registeredUsers.

Now I want to know how to create a new database dynamically so that it goes to blogContent database and not in registeredUsers database.

Here is how my server.js looks like:

const express = require('express');
const mongoose = require('mongoose')
const app = express();
const dotenv = require('dotenv')
const routesURLs = require('./routes/routes')
const registerRouter = require('./routes/register')
const loginRouter = require('./routes/login')
const blogRouter = require('./routes/blog')
const cors = require('cors')
dotenv.config()

mongoose.connect(process.env.DATABASE_ACCESS,{
        useNewUrlParser: true,
        useUnifiedTopology: true,
        useFindAndModify: false,
        useCreateIndex:true
    },()=>console.log(
        'database connected successfully'),
)

app.use(express.json())
app.use(cors())
app.use('/',routesURLs)
app.use('/register',registerRouter)
app.use('/publish',blogRouter)

app.listen(4000, () => {
    console.log(`Server started on port`);
});

This is my blog schema:

const mongoose = require('mongoose')

const blogModel = new mongoose.Schema({
    title:{
        type:String,
        required:true,
    },
    category:{
        type:String,
        required:true,
    },

    slug:{
        type:String,
        required:true,
    },
    description:{
        type:String,
    },
    content:{
        type:String,
        required:true
    },
    featuredImage:{
        type:String,
    },

    publishedAt:{
        type:Date,
        default:Date.now
    }
})

module.exports = mongoose.model('blog',blogModel)

And this is my blog.js

const { response, request } = require('express');
const express = require('express');
const router = require('express').Router();
const blogModel = require('../models/Blog')

router.post('/',async (req,res)=>{
    const blogArticle = new blogModel({
       title:req.body.title,
       description:req.body.description,
       category:"haha",
       slug:"some-thing-here",
       content:req.body.description,
    })
    blogArticle.save().then(data=>{
        res.json({
            data:data,
            message:"Hurray all done"
        })
    }).catch(error=>{
        res.json({
            error:error,
            message:"Lol! Nothing works"
        })    
    })
})


module.exports = router;

Note When I removed registeresUsers from the mydatabase string, every data goes to Test database.