[verb (plain)] + とすれば / としたら / とすると [i-adj] + とすれば / としたら / とすると [na-adj] + だ + とすれば / としたら / とすると [noun] + だ + とすれば / としたら / とすると
とすれば, としたら and とすると mean "supposing that…", "if it is the case that…": you take something as a premise and say what follows from it. They are the quotation と plus する in its three conditional forms, and follow the plain form of a verb or an い-adjective; a noun or a な-adjective takes だ first.
In writing, だ after a noun is often dropped: ひとり一人ごせんえん5000円とすれば.
All three can usually stand in for each other. The differences are of tone.
としたら is the most conversational, and the one for imagining: "if you could…", "if I were…". もし often comes first. とすれば sounds reasoned, the premise of a calculation or an argument. とすると draws a conclusion from something just learned: "if that's so, then…".Plain たら states a condition that may well come true. としたら makes it a supposition, something you are not sure of or that is unlikely.
These go beyond the conditional after a clause.