Hi @shyraza
The green cable in the photo you took is a coaxial cable from cable provider Ziggo, and you cannot use it!
You connect the KPN modem (Box 12) to a KPN fiber optic connection (FTU) (usually an orange fiber optic cable) in the meter cupboard or to the old copper network (ISRA point).
Have you requested a fiber optic connection from KPN?
And is there an FTU (fiber optic modem in your meter cupboard) that has an orange fiber optic cable in it?
Did you also find a black NT in the package, with 3 lights on it?
But the KPN modem (BOX 12) is connected with a UTP cable, from the connection to the WAN port (with fiber optic) in the modem.
For a copper connection this is the DSL port.