The option is present in Drive Setup under Custom Setup, but there is an easier way. Format as Standard. Then in the Finder, select the new hard drive. Go to the menu Special -> Erase Disk. There will be a pop-up menu that lets you select the drive format. By default it is set to HFS (Mac OS Standard). Pop it up and choose HFS+ (Mac OS Extended).
Oh, and you can convert an existing hard drive from HFS to HFS+ without moving your data off, but it takes
PlusMaker by Alsoft, a commercial utility. If you have the backup space, just backup & Erase Disc to HFS+, then copy back.