Making a colored 2D-image 3D

Hey!
How do I make a colored 2D image 3D? I have searched on youtube but everyone is using one-color images. Mine is using 5-6 different colors. I want it to have a thickness (look at example-images posted below)



Look at this https://www.youtube.com/watch?v=qo8kp8H7d_Q

or even this one that uses an online free online SVG converter https://www.youtube.com/watch?v=qsBhB-YdQHQ