Strong's numbers

ἅπαξ (G530)

hápax

hap'-ax

probably from ἅπας; one (or a single) time (numerically or conclusively):--once.

ἅπαξ, adv., [in LXX for אֶחָד, פַּעַם;]

(a) once: II Co 11:25, He 9:26, 27; ἔτι ἅ., He 12:26, 27; ἅ. τ. ἐνιαυτοῦ, He 9:7; καί ἅ. κ. δίς, twice: Phl 4:16, I Th 2:18;

(b) once for all: He 6:4 9:28 10:2, I Pe 3:18, Ju 3, 5 (MM, VGT, s.v.).†

From G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922), in the public domain.

Shown in the King James Version (KJV), whichever translation you read in — it is the text these numbers are tagged against.

Hebrews 12:27
And this word, Yet once more, signifieth the removing of those things that are shaken, as of things that are made, that those things which cannot be shaken may remain.
1 Peter 3:18
For Christ also hath once suffered for sins, the just for the unjust, that he might bring us to God, being put to death in the flesh, but quickened by the Spirit:
1 Peter 3:20
Which sometime were disobedient, when once the longsuffering of God waited in the days of Noah, while the ark was a preparing, wherein few, that is, eight souls were saved by water.
Jude 1:3
Beloved, when I gave all diligence to write unto you of the common salvation, it was needful for me to write unto you, and exhort you that ye should earnestly contend for the faith which was once delivered unto the saints.
Jude 1:5
I will therefore put you in remembrance, though ye once knew this, how that the Lord, having saved the people out of the land of Egypt, afterward destroyed them that believed not.