The program can be made Russian-language by taking the Russian language from ru.lproj.zip
So, you need to do the following: Copy the files from the "ru.lproj" folder to the "en.lproj" folder, overwriting the files contained in it. To do this, select copy files from the "ru.lproj" folder, then go to the Programs/Applications folder, select "Show the contents of the Parallels Desktop package", then go to Contents/Resources and paste the "en.lproj" files (you can do the same in, for example, pl.lproj, then you will need to select the Polish language in the settings). This will lead to the Russification of the program.