Depends ... did you convert the home to a rental ? Are you renting out part of your home while you are still living there ? If so the lesser of your cost basis or fair market value is used ... the program asks for both amounts.
What value are you seeking specifically? For what purpose? It matters.
The cost of your home is what you paid for it when you originally purchased it.
The FMV (Fair Market Value) of your home is what you could get for the property if you sold it today.
The tax value of your home is on your last property tax bill, and has absolutely nothing what-so-ever to do with the cost or FMV.