The query "Pixelmon ModPack.rar — prepare a paper" is ambiguous and could refer to several different tasks. To better assist you, please clarify if you are looking for help with one of the following:
Instructions on how to set up a Minecraft server using Paper (a high-performance server core) to host the Pixelmon Modpack for multiple players.
Help writing a formal paper , report, or documentation about the Pixelmon mod, its development, or its technical structure.
Steps to extract and manually install a modpack from a .rar file into your Minecraft directory.