According to Dell Precision T3600 specifications your computer only has internal SATA and SAS ports for storage. So, the new PCIe Gen3 x4 SSD will not work on your computer. Your computer has 2 x SATA 6.0GB/s ports. Regular SSDs run slower but the improvement of your system is amazing if you compare them with regular Hard Disk Drives.
Review the technical specifications of your pc.