Ok,
First of all thanks for everything. Really !
I’ve done the changes in function.php. I’ve switched the search engine from regular to index one. Added a {wcfmmp_store_name} and a {store_name} just in case but both are filled with stores names informations. The results don’t display the store name in the results.
Perheaps you’ll need my creditentials to log in my admin and see my function.php in my FTP ?