I trying to figure out what is the word for everlasting in 1st century Hebrew. All I’m finding is “Olam” but in first century Hebrew there wouldn’t be any vowels in it. And what would be the true meaning?

I don't understand your question for l'Olam is found already in the Torah both with a vav (vowel, e.g. Breishit 9, 12 and 16; 13, 15; 17, 7 and more), and without a vav (ibid 3, 22; 6, 3; Shmot 3, 15 and more).