Paint 3D is primarily used for editing and creating 3D models, but you can also start with a 2D image and apply a little magic to transform a 2D drawing into a 3D object.
Unfortunately, the process for this isn’t as simple as tapping a 2D to 3D button (wouldn’t that be awesome!). Converting a 2D image to a 3D model can involve copying parts of the image, using a brush to paint colors and designs, rotating and positioning objects, and more.
Select Canvas at the top. Drag the boxes around the canvas, or manually adjust the width/height values on the right, to ensure that the canvas can support not only the 2D image but also the 3D model.
This makes it much easier to sample the image so you can apply the same colors and shapes to the 3D model.