HiFiBerry and Pi 3B

Wich pins do i have to use as a minimum to use the hifiberry hat as a external dac? I tried 3, 4, 5, 6, 12 and 35, 38, and 40. No sound? wich do i have to connect to get sound?

HIFIBERRY DAC+, DAC+ ADC, DIGI+ AND AMP+, DAC2 PRO
GPIO2-3 (pins 3 and 5) are used by our products for configuration. If you are experienced with I2C, you might add other slave devices. If you a a novice, we don’t recommend this at all.
GPIOs 18-21 (pins 12, 35, 38 and 40) are used for the sound interface. You can’t use them for any other purpose.

On the HiFiBerry Digi+, GPIO16 is also reserved.

On the HiFiBerry Digi+ Pro GPIOs 5 and 6 are also used and cannot be used for anything else.