MAMP's phpMyAdmin username/password disappeared

After installing MAMP, I couldn't log in to phpMyAdmin because I didn't understand well and fiddled with databases and files.

http://localhost/MAMP/?language=Japanese

When I went to the above URL, the MySQL username and password were not displayed, and it looked like the following:

There is no problem with initializing MAMP, MySQL, or phpMyAdmin, so please tell me how to deal with it.