vapor barrier or not ?

beeginner

Hi,
Location is Central Florida .
Ripping out an old bathtub tile surround.
I'm going to just put up a tub surround.
2 walls are exterior ( cement block ) ,, and the remaining wall is studs where the plumbing is.
I plan just putting up Hardi Backer board and gluing the 3 piece tub surround to the
Hardi Backer board.
The 2 cement block walls have furring strips on them .
My questions are ,,,,
Can I just screw the Hardi backer board to the furring strips and glue the surround on ,,
or do I need some type of vapor barrier installed ?
Should I put insulated foam board in also ?
Any help is appreciated ,, Thanks ,, KZ