How to select information from a session user in mongodb?

Question

MongoDB

When sending the form for authorization, I check the user data, if successful, I write it to the session.
Next, I redirect to the user's page with his info.
As I understand it, it is necessary to write a session user to the store, and in the route, when getting to the user's page, you need to somehow select this particular user and there already in the database look for him and extract
Passport information, I do not use tokens.
The code is given, where I send data from the form during authorization

router.post('/login', (req, res) => {
  let { firstName, password } = req.body
  User.findOne({ firstName: firstName }, 'firstName userEmail password', (err, userData) => {
    if(!err) {
      let passwordCheck = bcrypt.compareSync(password, userData.password)

      if ( passwordCheck ) {
        req.session.user = {
          firstName: userData.firstName,
          userEmail: userData.userEmail,
          _id: userData._id
        }
        req.session.user.expires = new Date(
          Date.now() + 3 * 24 * 3600 * 1000
        )
        console.log('You are logged in', req.session.user)
        // res.status(200).send({ user: req.session.user })
        res.redirect('/login')
      } else {
        console.log('invaild login')
        res.send(401).send('incorrect password')
      }
    } else {
      console.log('invaild login')
      res.status(401).send('invaild login')
    }
  })
})