You need to read the instructions and follow them exactly. If followed, they do not ask for your passcode.
See the title that says "Remove your passcode"
See item 2 below that which says: "Make sure that your device isn't connected to your computer, then choose your device below and follow the steps:"
See the item 2 instructions for your specific model which states: "iPhone 6s or earlier, iPod touch (6th generation or earlier), or iPad with Home button: Press and hold the Side (or Top) button until the power off slider appears. Drag the slider to turn off your device. Connect your device to your computer while holding the Home button. Keep holding the Home button until you see the recovery mode screen."