The TC780 uses a specific multi-pin connector (different from the standard 2-pin K1 style). Look for a USB-to-TC780 programming cable .
Because HYT (now under the brand) has transitioned many of its legacy analog models to "End of Life" status, finding the official software can be tricky. Official Hytera Support
Open the CPS, go to "Setting," and select the COM port that matches your cable.