Alright, so look. This is one of the probably many ways you can do this. And this is how I used to do my stuff. So watch:
First change the mL to liters:
Orange Juice: 1L
Lemon juice: 550mL=0.55L
Soda Water: 2.6L
Apple cider: 2750=1500mL=1.5L
Then add them all together:
1+0.55+2.6+1.5=5.65
Lastly, multiply that number by 5:
5.655=28.25
Tammy will make 28.25 Liters of punch.
So Answer = 28.25 liters of punch