:welcome to Armaholic
First, some punctuation really helps to make your text readable and understandable. I don't understand the exact procedure you are following but let me try to give you some tips.
ok so im new to .pbo i downloaded the 31st infantry mod for arma2 i made the folders inside the arma2 file of my c drive when it was finished downloading it the folder came up in winzip automatically so extracted it to the addons folder i created
This archive already comes with its mod folder set up. Extract it into the root ArmA folder instead of extracting it in your custom created mod folder.
Unless you extracted all pbo files, and not the first folder.
i typed -mod= @31stwwa2 in the target box, computer asked me to verify and i did when i started the game nothing happened and it went on with the normal unmodded game, what am i doing wrong
I think you made an addons folder inside the mod folder and in the addons folder you added the 31th mod folder in which the addons folder is......and thats wrong.
is it winzip? do you absolutly have to use 7zip or winrar or equivilent, was it whati typed into the target?