Milk formula now comes in bags in the box not the normal tubs how can I store it any ideas x

Do formula now comes in a box in a bag instead off the tubs with lid so I'm wondering anyone been buying these and how are you storing once open I have seen on Amazon a one button formula container but it's pricey at 22 pounds for a container I would like something that would fit the whole 1.2 kg off formula powered in for convenience I use travel pots anyway in day but it's for the main formula , i was thinking could I just to out the old formula tub then refill but I'm thinking be traced off old formulas left behind etc. Also could use any container with lid but yet gain got to keep it dry cool and in dark place etc any one please x