"use strict";
//const { DataTypes } = require("sequelize/types"); // Remove this line

module.exports = {
  up: async (queryInterface, DataTypes) => {
    await queryInterface.createTable("dummytables", {
      id: {
        allowNull: false,
        autoIncrement: true,
        primaryKey: true,
        type: DataTypes.INTEGER,
      },
      id: {
        type: DataTypes.NUMBER,
      },
      first_name: {
        type: DataTypes.STRING,
        allowNull: false,
      },
      last_name: {
        type: DataTypes.STRING,
        allowNull: false,
      },
    });
  },
  down: async (queryInterface, DataTypes) => {
    await queryInterface.dropTable("dummytables");
  },
};

If you change the second line to;

const { DataTypes } = require("sequelize");

It should work fine.

A better fix would be to just install Sequelize like;

const Sequelize = require("sequelize");

then use it like;

first_name: {
    type: Sequelize.STRING,
    allowNull: false,
},

You might not even need to do the importation because up() would give it to you for free, You just need to replace DataTypes with Sequelize.

async up(queryInterface, Sequelize) {
    ...
}