There are two issues:

Module Namespace

For this, anything not likely to be ever used on CPAN is fair game. Using your company and/or project name is usually a good bet, e.g., AwesomeCo::Thingy, but anything that makes sense to you will do, really.

Module Installation

Let the module's Makefile.PL / makefile handle this; it will do the right thing, and makes it much easier to distribute. If your modules do not have a standard build structure, may I suggest the 8-year-old but still relevant José's Guide for creating Perl modules, which suggests Module::Starter and ExtUtils::ModuleStarter, in addition to h2xs. Pick whatever works best for you.

Even with existing module code, it is trivial to have one of the above utilities create a skeleton, and then you drop your existing code into the lib directory, and probably tweak the Makefile.PL and MANIFEST to suit (and hopefully add some unit tests!)