Macbook Pro Touch Bar 15 inch 2018 ssd Upgrade
It is not possible for ordinary users to replace the SSD in the 2018 MacBook Pro. You'll need specialized equipment and training in order to be able to replace the flash storage that is soldered directly on to the main board.

You can upgrade your storage by adding extra storage, such as for example a USB-C or Thunderbolt 3 connected external drive.