To convert to positive ground, you have to sort out the connections for correct polarity for the active device (your N JFET) and actual ground which will now be the positive supply rail.
Starting at the top, +9v will now be ground.
Volume pot ground will stay at ground. The 22n cap removes DC to the pot so polarity doesn't need to change. If that cap was are larger electrolytic, its polarity would need reversing.
The 1M gate resistor and the 1k5 source resistor change from ground to -9v to suit the N-channel device.
The 22uF source bypass cap reverses polarity and stays connected to ground. It could stay the same polarity and connect to -9v instead of ground, however, it must really connect to the true circuit ground via a low impedance path to that ground and that is now the positive supply.
The biggest change is due to the gate voltage now being referenced to -9v instead of ground, so we now have DC voltage on the circuit input that needs to be removed. So you must add a series input cap into the 68k "grid stopper", 10nF will do.
