On more than a few occasions, I have come across posts where folks “accidentally” delete one or more of the modules in the Module Manager or they do a “clean install” (that is, no Sample Data) and wonder why none of the Joomla! modules were installed.
Not to worry, there are all there and here is how to get them “back”:
Extensions > Module Manager > New (upper right) > … look! … there they all are! Just click on the one you want, set the parameters as desired and “Save”.
If you do a “clean install”, then all that will be shown in the Module Manger is a lonely instance of the type mod_mainmenu. You will have to go through the above-noted motions to get any and all the other ones that you require / want on your site.