Exegesis:

andres Nineuitai ‘the men of Nineveh,’ ‘the Ninevites’ (cf. v. 30).

anastēsontai ‘will rise,’ i.e. from the dead, or, ‘will appear,’ preferably the latter.

metenoēsan eis to kērugma Iōna ‘they repented at the preaching of Jonah.’ eis is best understood as equivalent to pros ‘with reference to,’ ‘because of.’

Translation:

This generation, short for, ‘the men of this generation,’ which often has to be used.

Repented at the preaching of Jonah, or, ‘repented because (or, when) J. preached (to them).’ For to preach see on 3.3.

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.