16 channels relay control with 3.3v pins
Based in the schematic and pictures, that board is hardwired without the typical jumpers. Four sections. 12V in and a builtin 5V regulator. The 5V powers the optocoupler led side. It also powers the optocoupler transistor side and relay driver side. Finally the 12v powers the relay section.

Some different relay modules have a jumper that let's you disconnect the optocoupler led side from the transistor side, and then you could power that side from 3.3v instead. But the pictures and the schematic don't show that.

In this case, you can either cut a trace and inject 3.3v at the optocoupler,  or use a transistor plus resistors for each input. As is, it will not work directly with a 3.3v gpio.