There is no cheat code to spawn a parachute in Grand Theft Auto IV. Unlike San Andreas or GTA V, GTA IV's cheat list omits parachute spawns entirely.
Enter IWPRKZ on the in-game phone (dial pad) → spawns a Duster (crop duster plane) which has a parachute. Exit plane → deploy chute. Does not work on PS3/Xbox 360.
Best bet: PC + trainer. On console: hunt helipads or accept the game's design—parachutes are rare, earned tools.