For If law is not made, then those men will be harmed to flee (those men) to another place.
Is this correct?
Again, JM, the rule of thumb is: If it doesn't make sense to you, then it can't be correct. (-:
ἥκοντες: present participle, masculine plural nominative, of ἥκω, to be taken together with εἰς τὴν πόλιν. Don't confuse it with the adjective ἕκοντες.
ποτε = "at some time," "once."
τοὺς ἄρχοντας: masculine plural accusative of ὁ ἄρχων. It is the direct object of πείσειαν.
θῶσι: third person plural, aorist active subjunctive of τίθημι. Its object is τοῦτον τὸν νόμον.
βουλήσονται: from βούλομαι, not βλάπτομαι.