What do i do when my phone say external media unknown state ?

Try removing the sdcard and then reinserting it, if that does not work if you can put the sdcard into another device(laptop,tablet,PC) to verify that the sdcard is working. If you get an error on the PC then your sdcard has gone bad if it works in your pc then most likely the phones sdcard slot is malfunctioning(check to make sure the sdcard slot is not dirty) Try removing the sdcard and then reinserting it, if that does not work if you can put the sdcard into another device(laptop,tablet,PC) to verify that the sdcard is working. If you get an error on the PC then your sdcard has gone bad if it works in your pc then most likely the phones sdcard slot is malfunctioning(check to make sure the sdcard slot is not dirty)