Microcenter shows us how clone the original SDD, open up the device and insert the new Legion Go SSD. In order to upgrade your Legion Go you need to get a compatible NVME 2242 SSD and an enclosure to clone the original SSD that comes inside the Legion Go.
Legion Go SSD Upgrade Recommended Parts
You can buy NVME 2242 SSD’s on Amazon here.
You can buy a 2242 enclosure on Amazon here.