Hi I think I m 13 week 6 day pregnant but last day I had an ultrasound there was empty sac no baby no heartbeat and baby was 9 week is it misscarriag?

Yes. Should have baby with good heartbeat. Heartbeats are always seen at 6 weeks. This is a miscarriage, technically called a missed abortion.
Need to clarify. You need to contact the doctor who did your ultrasound to clarify the findings and the plan of care. If the gestational sac was truly 9 week size and no baby was seen then this sounds like a blighted ovum (miscarriage). You need to confirm with your doctor and determine if a D and C surgery is needed.