I need to know where to train, my Pokemon are, Greninja, lvl 61, Charizard lvl 65, Lucario lvl 61, Krookodile, lvl 59, Pikachu lvl 60, and Salamence lvl 58.
This should help you. The marchioness girls have Audinos which give tons of experience. Good luck!
At this point, you may choose simply to challenge the Pokemon league repeatedly. Eventually, the exp gained from defeating the elite 4 will allow you to defeat the champion. If you want to do level grinding, go to Victory Road and defeat wild Pokemon there until your Pokemons' levels are high enough.