friendly urls? how to

[eluser]metaprinter[/eluser]
i've been handed a completed site that the client now wants to
1. make the url's friendly
right now i have: http://www.example.com/user/products/ContainersCat/1
buth they want http://www.example.com/user/products/boxes/metal
http://www.example.com/user/products/boxes/cardboard

etc...
Can someone push me in the right direction on what i need to do here? ps. i have no idea what version of codeigniter this site was built on .

thanks