There are two major MAME4droid versions on Google Play:
Go to the Google Play Store and purchase/install (the paid version is highly recommended for controller support and no ads; the free version works but has limitations). kof 98 rom mame4droid
: Open MAME4droid to let it create its directory. Use a file manager like ZArchiver to find the path: Android/data/com.seleuco.mame4droid/files/roms . There are two major MAME4droid versions on Google