How to run that long cable from the trunk to the front?

Most of the interior trim has tabs that retain it, but you need to remove it in a sequence because they all overlap with each other. What cables are you trying to run? Power? Speaker? What radio are you replacing, can you re-use the factory wiring? I mean if you are trying to run speaker cables to the doors and such the factory already did that in many cases. If it's for a sub box or similar, then those can go in the channels under the trim. Give an idea of which side you want and what you plan to run, and we can see what info we can provide.

The big long cable that comes with the Metra Kit 99-5717.
This goes from the new Radio to the rear where the speaker's connector is (left side of the trunk).

You could use the factory wiring for the speakers unless you have a reason you want to run the other ones. The image shows the trim panels along the bottom and the numbers are the order of removal. The center post trim can stay hooked on the top and just snake the wires behind it.

Answer does not fit with this car. That was my original idea, but if you follow C2009 the connector at the original radio I got only four cables going to the trunk, I will need another four. This also means no radio (Antenna cable) but I don't care about all I want
is to play my MP3 music files.

C388a is the connector in the rear that connects to all four speakers.

Thanks for that photo, I just want to make sure there will be room
for the new cable and will not break any plastic holders.

If I had four free cables or that can be use from c2009 to the back, then the problem will solve, but I am not sure about that or may affect something else.