Exegesis:

elegen oun ‘then he said,’ ‘he said therefore,’ depending on whether oun is interpreted as continuative or inferential. The former is preferable.

tini homoia estin hē basileia tou theou, kai tini homoiōsō autēn? ‘what is the kingdom of God like, and with what shall I compare it?’ For the function of these questions cf. on 7.31. For hē basileia tou theou cf. on 4.43. For homoioō cf. on 7.31.

Translation:

He said therefore, preferably, “next, he said” (The Four Gospels – a New Translation), “he continued” (New English Bible).

For the wording of the two subsequent questions see 7.31, which is in the reverse order, however.

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.