my i pad screen is black and showing plug in sign and on the top is I tunes written and photo. how to restore it

my apple i pad model no A1397 EMC 2424 RATED 5.1V,64gb .I was not able to do i cloud back up nor I was able to update IOS 8.3.Yesterday I connected my i pad with i tunes to update my i pad to IOS 8.3 and two hours it was dowloading the update and then.there was a message that it is unable to update.and suddenly my i pad went black showing plug in sign and above showing i tune logo and it is written i tunes What should i do?