Can i be arrested if i find a wallet and don't turn it in?

Just becase it is "lost" does not mean it doesn't belong to someone. If you take anything of value and "convert it to your own use" you have committed the statutory definition of Theft.

The proper procedure is to turn the wallet in to your local law enforcement agency, who will issue you a receipt for it. After it is held a certain amount of time (the law varies from state-to-state), and no one claims it, the finder can take legal possession of it.