Dupont jumper cables are housed in a plastic compartment and are not meant to be extracted - rather cut, then crimped, a new header fitted and then slid into the plastic compartment. However, there are cases where you would perhaps want to transplant from a header to the other but you do not really want to get all the tools necessary to crimp all the cables.

One way to extract the individual wires is to slide a very fine pin underneath the little slice of plastic that prevents the wire to be slid out.

You do not need to lift the little slice too much - it is not rigid but flexible and will be easy to lift so do not use too much force. With the slice lifted, you can keep trying to pull the cable out - again, very gently because with enough lift, the wire should slide out fairly easy.

Finally, make sure to remove wire by wire - it is a meticulous process but it beats having to get all the gear necessary and wait a lot of time for your stuff to be delivered.