URL redirect

I have changed my websites structure a bit and some URLS have changed.

I don’t want to lose the existing traffic so I need to redirect the old links to my new links.

I followed the instructions in www.isitebuild.com/301-redirect.htm adding this line at the end of the .htaccess file:

# redirect 301 /index.php/aktinovolies-pilones-ipsilis-tasis www.home-biology.gr/index.php/ilektrika-...ilones-ipsilis-tasis

I also tried:

# redirect 301 /aktinovolies-pilones-ipsilis-tasis www.home-biology.gr/index.php/ilektrika-...ilones-ipsilis-tasis

and

# redirect 301 home-biology.gr/index.php/aktinovolies-pilones-ipsilis-tasis www.home-biology.gr/index.php/ilektrika-...ilones-ipsilis-tasis

Am I doing something wrong?

Is there another way to redirect my old URLS?

Or is there a way to preserve my old URLS even though my articles have changed postitions?

thanks

If the page is not present client will get 404-(NOT FOUND) error page.
Yes you can use .htaccess to redirect users from old non existing links to new existing, but we are not experts on subject of configuring .htaccess files.