Your post is unclear, Dagmar. Are you trying to buy $L with money that's in your $USD balance, or are you trying to cash out your $USD balance and send it to your PayPal account?
To buy $L with your $USD, I think you should be able to just do it, without having a credit card or PayPal account on file, as long as you aren't trying to buy more $L than you have money for. But maybe you do need a payjment method on file. If so, LL will always take the money first from your $USD balance, and then if more is needed, from your designated payment method.
If you are trying to cash out to PayPal (what LL calls a "process credit" transaction) then you must have a "verified" PayPal account. This means that the account has been linked to a credit card or a real world bank account, by following the verification steps on the PayPal web site.
I have been trying to buy l$ from india with credit card but it is saying.
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I'm buying Linden's WITH my Process Credits, why do I have to link my credit card to my SL to buy it
in Linden Dollars (L$)
Posted
I have been trying to buy l$ from india with credit card but it is saying.
We were unable to add your payment method.
Please go back to the cashier and try again.
Please contact Second Life Support if you see this error more than once.