Anti virus

There is no Apple anti-virus for the iPad, nor is one needed. I've never seen the FB app or website request this.

If Facebook has blocked your account, that's probably because your account has been hacked and used to send spam. That does not require malware, and in fact, there is no malware for the iPad at all (unless you have jailbroken it). You will need to take this up with Facebook, and make sure to change your password (if they don't require you to do so anyway) when the account becomes accessible again.