Pages cannot be found after import

Hi,

I export my catalog from a Joomla 2.5 and import it in my new website Joomla 3.1.5
I recover everything, categories and products.
I installed the photos and they show up very well.
BUT when I try to use the menus from the categories or from the products I always obtain the same result: Pages cannot be found...
Everything is on the website but this is not working. What can I do?
I give you the screenshots below. The third one is the error.

Thank you for your help!

Categories showing well

Yes: www.academiaplatonica.com

In fact I have just Hikashop on this website for now.
I will create a menu to see that.
I don't know what is SEF?

I just created a menu "Information" and an entry named "Western Union" connected to one page.
It works well.
So the problem is in Hikashop.

Any insight?
thank you for your help.

I tried to disabled the SEF as seen here:

I did that and that doesn't change anything.
When I click on my page test it works.
When I want to reach a product, that doesn't work and I have still the same message of error I already posted: "The requested page cannot be found."

Ok. I did what you said and it works now
The only remaining problem for now is: when you click on a product the screen get darker but the photo of the product doesn't show up.
Example: www.academiaplatonica.com/index.php?opti...e-of-life&Itemid=103

OK. Thank you! I will test from different navigators and computers.