How to unpack MOD?
How to open a .pkm file? If I want to translate

What should MegaMod 8.01 do?
You don't need to unpack the .pkm (which actually can't really be done, once a mod is all wrapped up in .pkm form, that's it, it's in its final form).
Instead, you need to get the StringTables, translate them, and then pack them into a mod that will have to be loaded above MM in your modlist in order to overwrite MM and apply the translated names and tooltips on top of the mod.
The stringtables for MM8 are available here:
u have to unzip zip files and unblock files. pkm's move to the banished WinData folder. start game and enable mods, EXIT GAME COMPLETELY after the game reloads with mods enabled. then restart game. failing to exit and restart will result in crash.
The question wasn't about unzipping and installing mods, but about opening the mod's code to access it and translate it I think Stiles Wink