I am a victim of identity theft and need some guidance.

My banks' fraud department told me there's a virus on my computer; the ones who stole my money can see everything I do and I should have a complete system scan; get rid of the virus and any malware then install an anti virus program. Thus my question. Which would be the best application to buy to accomplish this?

I was told I should do this myself. Otherwise it would be very,very expensive. In total I have 2 MacBook Pros; 1 MacMini and 3 iPads. I'm using a MacBook Pro right now and think it's clean,but want to scan it any, just to be safe.

I would appreciate any suggestion and thank you in advance for it.
Alice C