Securing aluminium greenhouse to pressure treated wooden base

Hello. New unbuilt greenhouse. Builder has made a concrete base with pressure-treated timbers fastened to it.  The greenhouse assembly instructions merely say 'attach greenhouse to base with 50mm screws' (not included). I'm not savvy about these things so I'd be grateful if anybody could advise me what TYPE of screws to use. There seem be dozens at the local superstore and the teenager working there had no idea.

Thanks!