Generate 3d Mesh from 2d drawing

Hello guys, I try to make a mechanic like in "Draw Climber", the most important thing is creating 3d mesh with collider by 2d drawing on grid from player, for example you draw a circle - and it spawns a 3d sircle with collider. I thought about spawning mutiple cubes like pixels to build some shape, but how to controll it via c#? I tried to find a solution, but there is only one and It's not for free. From where should I start?