If you were viewing the fingerprint scanner right side up with the JST connector on the bottom, the pin on the far left is pin 1
Fingerprint Scanner————— FTDI 3.3V
Pin 1: UART_TX (level 3.3V) ————— RX
Pin 2: UART_RX (level 3.3V) ————— TX
Pin 3: GND ———————————– GND
Pin 4: Vin(3.3V~6V) ————————– 3.3V