Shortboard for me.

Hello everybody!
I'm a new surfer, I started few days ago with some lesson on a longboard and I can stand, now I would like to buy a surfboard (I was a snowboarder too). I'm here in Australia for 3 or 6 months more and my objective is to stand on a shortboard and it doesn't matter how hard it will be! But as a new surfer I don't know which is the correct size for me. I think as a beginner is better for me something bigger and thicker but I'm not sure.
Have somebody some advise of me?
I weight 137 lbs (62 Kg) and I'm 5.7ft (173 cm) tall.
Thank you!

I'm a new surfer, I started few days ago with some lesson on a longboard and I can stand, now I would like to buy a surfboard (I was a snowboarder too). I'm here in Australia for 3 or 6 months more and my objective is to stand on a shortboard and it doesn't matter how hard it will be! But as a new surfer I don't know which is the correct size for me. I think as a beginner is better for me something bigger and thicker but I'm not sure.
Have somebody some advise of me?
I weight 137 lbs (62 Kg) and I'm 5.7ft (173 cm) tall.
Thank you!