Connect 4x4 keypad to esp8266 I2C
4 x 4keypad needs 8 pins and the I2C back pack you have also have only &quot;8 port pins&quot; which you can use.
The remaining 8 pins are power, I2C address and interrupt pins.


In the image, the orange color goes to the keypad matrix, the purples ones are static (power, address config.), you connect it once and leave it and the green ones are the lines to be connected to Node MCU.
As @Michael mentioned, you can use same I2C lines for both LCD and Keypad backpack.. Just make sure that I2C addresses are unique.
A0, A1, A2 can be used to change the I2C address. Please read data sheet of PCF8574. Ask again if you are not sure still.