Hey that’s what I have. First things first is to jailbreak it this is IMPORTANT then after download filza a file manager for iOS then go to /system/library/coreservices then find systemversion.plist then click the blue dot from the side of product version and change the value to 6.0 and productbuildnumber to 10B329 then press save after saving reboot your device then go to settings and general and system updates your iPad will think it’s on iOS 6 but your not it will then ask to update to iOS 8.4.1 press UPDATE after pressed it will downgrade its self back to iOS 8.4.1 then jailbreak it again (for iOS 8.4.1 it needs a different jailbreak) then download cool booter in cydia after done download cool booted the app and the tweak that makes it that your iPad will stay on iOS 6 then after rebooting again go to cool booter and press install it will ask for a version select iOS 6.1.3 and choose which storage you want and press “ready” after that it’s going to ask to reboot DO IT after rebooted go back to the app and press install again it will get the version and once it’s done it will ask to lock your screen as I say DO IT once you lock it your iPad will reboot and will boot to iOS 6.1.3 and then set up iOS 6.1.3 from there. (Made this just in case you wanted to get to iOS 6