He just want to claim that free UniSwap tokens for you ... sell him your wallet used for uniswap trading and he will claim free 400 uniswap tokens ... It's that simple.
How much do they pay for those garbage tokens these days?
Today 5$ for one token. There was a moment in history they were priced 40$ each.
Still claiming 400 tokens x 5$ ... you get 2000$... If he buy a wallet even for 500$ its still great business.