When you talk about all the files to your iWeb sites, then what files do you mean? You need to be more specific here, because in the past, people have the made the mistake of saving incorrect files - there were the domain.sites files where iWeb stored all its data or you have the html files.
Unfortunately, there are very few web creation packages that can import sites and of those that can, they are complex and not like iWeb at all and have a very steep learning curve.
The two that can would be Flux V and DreamWeaver, both of which are quite complex and you need to know html and css to get the best from it.
You will never find anything that can both import and is as easy to use as iWeb - it does not exist.
Also, it is not a good idea to even try importing an iWeb site - it is so bloated with html code that in the long run, it would just be easiest to purchase another package that you are comfortable with and start from scratch and re-build your sites.
The one that is most like iWeb isEverWeb Click on the link and take a look.
Unfortunately, you will be hard pressed to find anything that fits your needs - it would be quite complex.