Hi jincheol,
Thanks for reaching out to Apple Support Communities. It sounds like you have a question about switching keyboard layouts on your iPad. We're happy to help.
"On iPad, you can turn typing features, such as spell checking, on or off; add keyboards for writing in different languages; and change the layout of your onscreen or wireless keyboard."
You can find this information and other helpful details in the guide here: Add or change keyboards on iPad
Additionally, if you need help setting up your Magic Keyboard check out the steps here: Set up and use Magic Keyboard for iPad
Best!