Virtual disks in vSphere always consist of two parts, a small header/descriptor file (a text file), and the data file. For most tasks - including the conversion - you will have to use the header/descriptor file (which contains a reference to the data file). The conversion you should result in a single .vmdk target file, which you can then upload to the vSAN datastore. This task will split the stream-optimized file into a header/descriptor file in the VM's home object and the vSAN virtual disk object.
André
