Arduino Mega 2560 I2C Pins?

Hello people, I'm trying to control a rotary encoder via a MCP23017 chip. I just replicated this example but it doesn't work, I guess it's due the I2C pins are different in my board. Could someone please tell me what pins should I use? Specs says 20 and 21 but those are chip pins not board, right? Thanks in advance!

Edit: nvm i found it, it's even printed in the PCB :-*

I'm trying to control a rotary encoder via a MCP23017 chip.

A rotary encoder is an output device. What do you mean by "control" with respect to an output device?

TWI: 20 (SDA) and 21 (SCL). Support TWI communication using the Wire library. Note that these pins are not in the same location as the TWI pins on the old Duemilanove or Diecimila Arduino boards.

Specs says 20 and 21 but those are chip pins not board, right?

They are board pins.