You can do that by opening the profile manager and using the options in the profile manager to delete the profiles. For details of how to do that see https://support.mozilla.com/kb/Managing+profiles

When removing a profile only delete the files if you stored the profile in the default location. If you stored them elsewhere, you can end up deleting files other than the profile files. If you want to play safe, when using the profile manager to remove a profile, do not let it delete the files, you can then manually delete the files.

Do those profiles store the add ons and extensions as well? I want to get rid of visited websites as well. Are they located in those too or somewhere else?

User installed extensions are normally stored in the profile folder. All user data such as bookmarks, password, history, cookies is stored in the profile folder.

You can create a new profile folder and it will have no extensions, unless you have installed any global extensions. A new profile will be be similar to a new install.

I did all that and added an extension (ad block plus) which before the deletion of the profiles appeared on the top next to the bookmark button on the right near the home button. after re install it now shows in the add on toolbar at the bottom. Is there a reason for that?