Upgrading a simple drupal 7 module to drupal 8?
I've spent the past few months doing a lot of D7 -> D8 upgrades. I haven't used sub_name (or even seen it), so I cannot comment on that, but as for the path, it's the same path you declared as the array key in your hook_menu definition - however note that with D8 you need to include the preceeding forward slash.

So if your D7 hook_menu() definition for a path was:

$menu['path/to/something']


In D8 your path in the routing file would be:

path: /path/to/something