Redirect old permalink structure to the new one

I have used for a long time the permalink structure below;

index.php/year/monthnum/day/postname/

and now, i move my site to a new hosting and decided to change the structure;

/postname

As you can guess that a lot of people link my site with the first(old) structure so i’m losing so many visitors now 🙁

How can i redirect the old url to the new one?

I tried a lot of .htaccess – Mod_Rewrite thing but it didn’t work. I think i’m doing something wrong.

Any suggestion?

Thanks.