Really, really confused and could do with some straight answers, so please help

I am booking a holiday for Oct

The flight will be approx 5.5hrs so she will be due milk in that time. What is the best option:
1. Take powder milk and add bottled water, if so what water is recommended??
2. Ready made formula milk
3. Can I take food in jars?
Really unsure and would appreciate some help.
Thanks so much
Peggy