The front audio and microphone connectors are specified as: MIC IN (R) // MIC POWER (L) // LINE OUT FR AND LINE OUT RR // LINE OUT FL AND LINE OUT RL but on the Intel DG31PR motherboard is As in the figure below.

how should I proceed?

It's a standard FP_AUDIO connector.
Since some audio chips allow switching/repurposing MIC input as an audio output, it is simply marked as "port", not "mic" in intel's user manual.

Under the normal circumstances the pinout looks like this:


The PF_Audio connector has been the same for many years and there is no way you can plug it incorrectly.

I already figured out how to connect the panel cabling to the motherboard connector, on 02/01/2017 post the result, ok