King James Version (KJV)
He smote also all the firstborn in their land, the chief of all their strength.
Modern English
He struck down all the firstborn in their land, the firstfruits of all their strength.
Hebrew
וַיַּ֣ךְ כָּל בְּכ֣וֹר בְּאַרְצָ֑ם רֵ֝אשִׁ֗ית לְכָל אוֹנָֽם׃
vayak kal bkvor bʾarṣam reʾshiyt lkal ʾvonam
כָּלkolevery / all