Get Message By ID: Discord.js

fetchMessage is no longer present in Discord.js starting in version 12, but you can use the fetch method of the MessageManager class from the messages property of the TextChannel class.

msg.channel.messages.fetch("701574160211771462")
  .then(message => console.log(message.content))
  .catch(console.error);

You can retrieve a message by id through

msg.channel.fetchMessage();

The documentation is here. If you want to be able to retrieve a message from any channel by id, you can loop through all channels and catch any errors.