What you need to do is, open Inkscape and import the jpeg image (file>import). Then, making sure you have the image selected, do Path>Trace Bitmap. Click the 'Colors' option and press OK. It might take a long time depending on how fast your computer is and how large the image is. Then delete the origional image you imported - it will be underneath the newly vectorised image.
What you'll have there is Inkscapes (usually pretty good) attempt at converting each colour section of the image into a vector. Try it out! Change the settings and see what happens