A standard K-Plug (Kenwood-style 2-pin) USB data cable.
Open the software, select the correct COM port, and click "Read from Radio" to back up your current settings before making changes. Key Specifications of the FC-136 Specification Frequency Range VHF: 136–174MHz Channels Up to 128 programmable memory channels Connectivity K-Plug (2-pin) for data and audio Configuration Software-only (No manual frequency input) Firstcom FC-136 Manual and Specs | PDF - Scribd
Before connecting the radio, install the USB-to-Serial driver (often Prolific or CH340) for your programming cable.