late 2013 mac pro internal ssd adapter

a similar card by Sintech is the most trouble free and most often recommended adapter for the Mac Pro late 2013 desktop. I think it may be this one:

https://www.amazon.com/Sintech-Adapter-Upgrade-2013-2016-2013-2015/dp/B07FYY3H5F?psc=1&pd_rd_w=ODdVG&content-id=amzn1.sym.56b6d1e1-8781-4e32-a7bc-5298ad4b88ac&pf_rd_p=56b6d1e1-8781-4e32-a7bc-5298ad4b88ac&pf_rd_r=VTRXBZ0KQ8TD218SAJSX&pd_rd_wg=y7THL&pd_rd_r=13d11b8e-f1b3-463f-a17a-c6391e27d10c&ref_=sspa_dk_detail_1

-OR-

OWC/MacSales sells a kit with their direct replacement drives for this machine. They pride themselves on the Mac-focused support.

NB>> You MUST have already installed High Sierra before making the changeover, so that you can be certain you already installed the firmware version required to BOOT off the new drive.

That firmware update is not stored on the drive -- it is placed in a private store on the processor card.

As far as I can remember you need a PCIe adapter than can hold a standard SATA SSD.