I'm sorry, but if you mean N64 graphics as in 3D graphics on the level of N64, those are pretty much impossible to do on SmileBASIC (for 3DS). Even 3D on the level of SNES is tough to get right. However, there are some engines that facilitate creating 3D worlds and models, such as the raycasting engine and P3D. I'd suggest either looking those up or reconsidering the graphics style...