Citroen C4 2006 2.0 HDi DPF Fluid Bag Replacement

Hello Friends,

Do you maybe have some manual for replacing bag (I think it is bag, not a tank)?
Engine is 2.0 HDI 136HP, 2006 year. What is the best way to check if it is bag or tank to refill?

I am a newbie with DPF's, only one time I have refilled the tank in C5.

Thanks.