Hang on while I ask my Mum…
Apparently it was either Snow White and the Seven Dwarfs or Dumbo.
The first movies I remember seeing were in 1980-81.
Herbie Goes to Monte Carlo
The Muppet Movie
Star Wars
The Empire Strikes Back
Herbie Goes Bananas
Popeye
Lady and the Tramp
Condorman
Battlestar Galactica
Flash Gordon
E.T.
The Smurfs and the Magic Flute
I also remember seeing The Wizard of Oz on TV around then.