The 2014 MacBook Pro 13-inch uses a proprietary blade SSD

The 2014 MBP 13-inch uses a proprietary PCIe 2.0 x4 connector with a 12+16 pin blade-style drive. It’s not a standard M.2 slot, so you can’t just drop in any NVMe drive — but third-party adapters exist if you’re willing to tinker.