Have a private nintendo bought and do not know a pin of it jmd if I can somehow reset it by pc?

So I bought a nintendo 3ds via shpock but immediately realized that it was not working as it should, the seller told me to just remove the pin at this age I did not know that you ALWAYS need it and forgot it " nothing can help me and tell me how I get it formatted as a button combination or maybe with the computer I do not want to have paid in vain and the nintendo support has so private sales no guarantee so they are also out I'm happy about each Thank you very much in advance

Per PC not easy, yes yes google 3DS reset or something

Have to contact the customer service, who then tells you what to do.

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