Unless this prebuilt came with something special for the m.2 it would be better to take advantage of what are still great price to performance options on new NVME drives. Especially in light of the great suggestions above to include a clean install.
And if your important data is only stored in one place, fixing your lack of a backup solution is way more crucial a situation than worrying about a new PC. Data stored in one place will eventually be stored in no place.