You can very easily calculate how long it would take you to find a block knowing the hash rate and network difficulty. The formula (at least the simplified version) is:

Difficulty * 2^32 / hash rate = time to solve a block (in seconds)

6 S7s (batch

gets you 28.38TH/s. Current difficulty is 65848255179. If you had those miners right now, we can see that it would take you:

65848255179 * 2^32 / 28380000000000 = 9965331.30699322149345

So, 115.34 days to solve a block. Therefore, you've got about a 26.01% chance of finding a block in 30 days with that hash rate ... assuming it was mining right now. As soon as the difficulty changes, that value changes as well.