Thanks for your reply.
I am not splitting the documents. I am writing different word file and ten merging in one bigger.
I am writing a scientific paper
file 1 : Intro
file 2 : matherial and metods
file 3 : results
etc etc

when I copy all in one file, do the photos number, captions and table automatically update?
for example I have 1 img in file one (FIg.1) and I have one img in file 2 (Img.1).
If I copy and paste the text from file 2, not that img is image 2.