You can only hold any crypto you buy through the Venmo app. This means you cannot move it to another wallet or exchange. As of right now, Venmo only offers the ability for users to buy, sell and hold 4 different cryptocurrencies through its mobile app. You can't use crypto to get paid or send payments at this time, and you can't transfer it to other accounts.
Venmo also doesn't provide a private key when you but crypto through the app. The purpose of buying digital currency like Bitcoin through Venmo is that it's very easy. Just log in to your account and purchase the amount that you want. You don't have to worry about losing your key or theft, as Venmo promises to protect you crypto like it would your cash.You can learn how to purchase crypto through Venmo at this link.