Back in 2017 I purchased a 27" "Core i7" iMac, and opted to get the storage upgrade giving it a 500 GB SSD instead of a hard drive or fusion drive. I'm now considering upgrading the storage, but I'm not sure if the drive is a conventional SATA SSD or a "blade SSD" (to use iFixIt.com's terminology) that uses a proprietary connector, which I understand to be similar to but different from NVMe. The upgrade procedure is quite different depending on which it is.
How can I tell what kind of SSD my iMac has?