He wanted to harvest their "essence" to become more powerful and invincible with a wand powered by smurf magic :)
The Wizard Is Called Gargamel in the smurf movie that was realeased last year. Hope this helped.
Smurfs - 1981 Gargamel's Quest Gargamel's Second Childhood 7-36 is rated/received certificates of: Australia:G
Gargamel .
Gargamel and his cat, Azreal.
Smurfs - 1981 For the Love of Gargamel The A-Maze-ing Smurfs 2-17 is rated/received certificates of: Australia:G
Gargamel
Smurfs - 1981 Gargamel's Sweetheart 7-6 is rated/received certificates of: Australia:G
Gargamel.
Gargamel
Smurfs - 1981 For the Love of Gargamel The A-Maze-ing Smurfs 2-17 was released on: USA: 23 October 1982 West Germany: 26 July 1984 (segment The A-Maze-ing Smurfs") West Germany: 2 August 1984 (segment "For the Love of Gargamel") Netherlands: 14 August 1984 (segment "For the Love of Gargamel") Netherlands: 13 October 1984 (segment "The A-Maze-ing Smurfs")"
Smurfs - 1981 Gargamel's New Job 6-3 is rated/received certificates of: Australia:G
Smurfette was created by Gargamel to trick the other Smurfs, but Papa Smurf then made her into a real Smurf.