Since my cervix is high during O, if I used a 3ml syringe for AI, will I still be able to get pregnant or do I need a 10ml syringe?

Artificial reproduct. Personally, I'd recommend that you consult a Reproductive Endocrinologist for artificial reproductive techniques (ART). But given costs for this elective stuff, I can understand why you might consider DIY project. Unfortunately, there's no study proving that 10mL is better than 3mL syringe for specific body types (or cervical placement), so there's only one way to find out. In meantime, have fun!