Your piggies should have as much floor time as you can give them, but ideally a few times a week. If their cage is only meeting minimum sizes then they will need to come out more often - if their cage is larger then they may be fine with coming out a few times a week.
I’m assuming you’ve got three sows - three sows together need a cage of 180cm x 60cm, or a 2x5 c&c cage (Which measures 180cm x 77cm).
how you can make it bigger depends hugely on what your current set up is.
That’s a good amount of floor time
if your cage is a 2x8 then that is plenty big enough for three sows and wouldnt need to be made bigger. With a cage that much bigger than the recommended size of 2x5 then they have plenty of space to get plenty of exercise within the cage