I have seen a couple of T3500 and they have a 6-pin power connector.
You should check the PSU on yours to make sure.
Some RX570 have 6-pin and others 8-pin power connector.
Make sure to get the right one for your system.
The T3500 has a 525w PSU and it has a single 6 pin PCIE connection.
24 Pin, 8 Pin 12V, Floppy Drive, SATA I, 6 Pin PCI Express, 4 Pin Peripheral, 4 Pin 12V, 6 Pin Auxiliary