What cheat code do you use for spruce wood in Minecraft?

The last argument to /give is the numerical "block id". You can look up block ids on any of the various Minecraft wikis. For example, http://minecraft.gamepedia.com/Spruce_wood#Data_values shows that Spruce Wood is block id 17.

This command is just like giving yourself wood which would be /give @p wood but to give yourself spruce or birch ext you would do /give @p wood 1 1 or /give @p wood 1 2.

It is

/give <player> <item> <amount>

For example, if I wanted 6 iron ingots, and my player was Jeff, I would write:

/give Jeff iron_ingot 6

Warning: Do not make the item plural otherwise it won't recognise the object.

As of the newest versions of the game, your answer would be

/give [USERNAME] minecraft:spruce_planks [COUNT]

This is the more simplified version. It appears you, after about 4 years, should know how to get spruce planks by now, but this answer is to clarify for any new visitors wondering the same thing for newer versions.

give @s log 64

I don't know if it's different for other versions, but this is for 1.12.