How much are my DSi and DS games worth at gamestop?

I just need an estimate, I have: a black DSi in great condition, Kingdom Hearts 358/2 Days, Mario Kart DS, Super Mario 64 DS, Mario & Luigi: Bowser's Inside Story, Professor Layton and the Curious Village, Brain Age, Legend of Zelda: Phantom Hourglass, Pokemon Platinum and Scribblenauts. And, any suggestions to sell my games elsewhere that is not online.