Welcome to the forum
Could you tell us what sexes and ages the piggies are please?
This will have a bearing on our advice going forward - for example, if they are all male, then they cannot be put together at all (boars can only be kept in pairs). If you were to attempt to four males in one cage you would end up with fights and potentially all four of them falling out and having to live in four separate cages as it can break all bonds.
If they are all sows, then they can in theory live together but whether they actually will is another matter. They can only go together if they are compatible. Older bonded sow pairs are less likely to want their pairs disrupted so they also may never want to live together. If they are younger, you have a better chance but again its down to compatibility so there is no guarantee, but it’s also easier if one pair is younger than the other.
The recommended cage size for four sows is 7ft x 2ft (210x60cm).