Answer:
≈ 4614 mL
Step-by-step explanation:
I'm guessing you want to add them. So, let's convert them all to mL first and then add them!
3/4 gallons (U.S. I'm assuming) ≈ 2839 mL OJ
3 pints (U.S. I'm assuming) ≈ 1420 mL GA
1.5 cups (U.S. I'm assuming) ≈ 355 mL PJ
Add them up and you get around 4614 mL of a disgusting mixture of juice. I hope this is what you were looking for!