Differents urls after migrate to J3

Also i see that the menus do not exist in the migrating site:

j3.impactance.fr/Management-Communication/

does not exist

?? Why menu does not exist ? As i migrate from 2.5 update Joomla Update (tried Micker advice to do this as he was really confident in his post), all should be the same in the menu, no ?
I try v3.0.15 right now.
Thanks Georges

3.0.15 installed. No changes on urls...
What can i do ? Use a url rewriter ? (the goal is to avoid to loose all indexed urls in Google)...

Ok,
I can get what i want with a tool like sh404.
This solve my problem but this not solve my question : i would like to avoid tools like sh404 to use Flexicontent router but the result is not the same at all : Flexicontent url rewriter show me things like "item" or number and that's not so good for seo work.
Thanks for the help on this post : again, problem solved for now, but it will raise in the future...
Xavier

Hello

but you have not answer me,
- have you checked if the menu item exists

Also
- are both sites using SH404SEF or they are not
- did you upgrade to J3.5.1 or to J3.6.0-RC ?

So,
- menus are exactly the same,
- Sh404 are in use on the site to get the same urls
- i did upgrade with the rc version.
Thanks for your time Georges