John 3:12

εἰ τὰ ἐπίγεια εἶπον ὑμῖν καὶ οὐ πιστεύετε, πῶς ἐὰν εἴπω ὑμῖν τὰ ἐπουράνια πιστεύσετε;

Rough Word-by-word:
If the on earth [things] I said to you all and not you all believe, how if I might say to you the on heaven [things] will you all believe?

Smooth Translation:
If I said to you earthly things and you all do not believe, how will you believe if I might say to you heavenly things?

εἰ conditional conjunction "If"

τὰ definite article accusative neuter plural "the"

ἐπίγεια adjective accusative neuter plural "on earth/earthly"

εἶπον verb imperfect active indicative 1st singular from λέγω (I say) "I was saying"

ὑμῖν pronoun dative 2nd plural "to you all"

καὶ conjunction "and"

οὐ negative particle "not"

πιστεύετε verb present active indicative 2nd plural from πιστεύω (I believe) "you all believe"

πῶς adverb "how"

ἐὰν conditional conjunction "if"

εἴπω verb aorist active subjunctive from λέγω (I say) "I might say"

ὑμῖν pronoun dative 2nd plural "to you all"

τὰ definite article accusative neuter plural "the"

ἐπουράνια adjective accusative neuter plural "on heaven/heavenly"

πιστεύσετε verb future active indicative 2nd plural from πιστεύω (I believe) "will you all believe"