There is only one file type that uses the .MCPACK extension:
Minecraft Resource Pack File
An MCPACK file contains resource files that modify Minecraft (Bedrock Edition), a popular block-building game. It stores multiple resource files, such as .PNG and .JSON files compressed with ZIP compression. MCPACK files are typically used to transfer resources between Minecraft users.
The resources stored in MCPACK files may be used to alter gameplay or the Minecraft UI. They may also add seasons to the game, alter graphics, modify characters, and optimize graphics.
Since MCWORLD files are saved in a .ZIP format, they can be expanded using a Zip decompression utility. Simply rename the ".mcworld" extension to ".zip" and use a zip decompression program to expand the contents. You can then view the contents. Some Zip programs include Corel WinZip, 7-Zip, Apple Archive Utility, or ES File Explorer.
Updated: January 17, 2019