Venmo currently is able to send payments to PayPal accounts from sales. If you want to transfer money from Venmo to PayPal, you have to do it through a bank account that's linked to both of your Venmo and PayPal accounts. Withdraw Venmo funds to the bank account and then add those funds to your PayPal Account via the "Add money" link and choose the same bank account to top up your PayPal Account.