[Vuejs]-Load Nuxt project to exist express app

Yes, it’s possible. See official nuxt template -> https://github.com/nuxt-community/express-template

Or you can use something like this

const { Nuxt } = require('nuxt')
const config = require('./nuxt.config.js')
const nuxt = new Nuxt(config)
const app = require('express')()
app.use((req, res) => setTimeout(() => {
  return nuxt.render(req, res)
}, 0))
app.listen(port, '0.0.0.0')