The easiest method is to find dedicated comic conversion software on the internet. Many of them have simple instructions that guide you through the process of converting comics to cbz. Just make sure the software is reliable and compatible with your comic files.
CBZ is often preferred for comics as it's a simple archive format that retains the original image quality. Epub might reformat the pages, which could affect the comic's layout.
If you want to choose an iPad that is more suitable for reading e-books, I suggest you choose the iPad 4. Although the iPad mini also provided e-book reading function, its small screen size might be difficult to read e-books for a long time. In addition, the processor and storage capacity of the iPad mini were not as powerful and sufficient as the iPad 4.
The iPad 4 is equipped with a retina high-definition display to support high-resolution e-book reading. It also supports a variety of reading modes such as full-screen mode and landscape mode to better adapt to different reading postures. In addition, the iPad 4's processor and storage capacity are powerful enough to support a large number of e-book applications and reading applications, including Amazon e-books, iBooks, Google Play Books, and so on.
Therefore, if you want to choose an iPad that is more suitable for reading e-books, it is recommended to choose the iPad 4.
I'm not sure about specific places to download manga in CBZ format. You might try some manga-related forums or communities to see if anyone there has suggestions.
You can usually do it through the settings or preferences option in the relevant software or platform. Just look for a 'folder management' or 'add folder' option.
It provides some resources on Arctic wallpapers and backgrounds for iPad devices. These resources include high-definition, high-quality polar bear images and aurora borealis images, which can be downloaded for free and displayed on the iPad desktop.