We've inherited a VM ESXi server running SSD on a Dell Perc 730 card.
The datastore in VMware is set to be non-ssd.
The server itself is running fine, in fact it's very good indeed, so what are the pressing reasons to convert the datastore to SSD? Should we even do it? What will it give us.
Have a look on these KBs, sometimes controller doesn't recognize disks as SSD. SSD drives are usable for vSAN and caching.
SSD Not Being Detected in vSphere ESXi 5.x | Dell India
Configure SSD on Dell PowerEdge with PERC - vInfrastructure Blog
Nothing needs to be done. You are running a RAID card which isn't going to show up as SSD. If you had a single SSD that you wanted to use for Flash Read Cache, then it would be important. But that won't work with your setup.