Can you use your old Sd memory card on a new Nintendo switch

Hi, I’m after a little help please, not very clued up on the Nintendo switch and how it all works, I have a old switch and 2 sd cards with paid for games on, I have just purchased the new improved battery switch and wanting to put my sd cards in but it’s saying I can’t use it in my new switch as it’s been used on another. But the thing is I want to sell my old switch and reset it all to factory settings so nobody can get my details or my already purchased games, so how can I get my sd card to work on my new switch, I’ve tried to log in on my new one but I can’t even manage that, sorry for all the questions but I’m feeling frustrated now as looks like I’ll be lumbered with 2 switch consoles now but only need the one. All help in simple terms will be most appreciated