It’s asking for an able account number. I’ve never had to use it before. What is it? How do I access the number ???

You can find your ABLE account number at the ABLEnow website; or, depending on your state, you can find it through your state's ABLE website. 

Achieving a Better Life Experience (ABLE) accounts allow the families of disabled young people to set aside money for their care in a way that earns special tax benefits. ABLE accounts work much like the so-called 529 accounts that families can use to save money for education; in fact, an ABLE account is really a special kind of 529. 

See this TurboTax tips article for more information about ABLE accounts and when you need to report them on your tax return.