Since you have apug with an integrated hanger, you must have a mid to high end bike. Early PAs, PRs and PXs have a hanger that is designed to accept only Simplex derailers.
You have three choices:
1. Sell the Suntour and buy a Simplex derailer that fits your hanger. The SX610 and SLJ6600 drop parallelogram models shift the best. The SLJ will be very expensive. The SX will just be expensive.
SX610
SLJ 6600
2. Modify your hanger to accept the Sintour. I did that to my PX10. I wish I hadn't.
3. Cut off your hanger and mount the Suntour with a bolt on mounting claw. Resist the temptation to do that!