The past tense of turn swords into ploughshares is turned swords into ploughshares.
The third-person singular simple present indicative form of turn swords into ploughshares is turns swords into ploughshares.
The present participle of turn swords into ploughshares is turning swords into ploughshares.
The past participle of turn swords into ploughshares is turned swords into ploughshares.