In New Testament times, the expression to be "lifted up" is an euphemism to refer to being crucified, i.e. to be nailed to a cross and be lifted high up to die.
Our Lord Iesus used this term when talking to Nicodemus in John chapter 3 and again to the Pharisees in John chapter 8, as shown in the verses below:
14 As Moses lifted up the serpent in the wilderness, even so must the Son of Man be lifted up, 15 that whoever believes in him should not perish, but have eternal life.
John 3:14 World English Bible
28 Jesus therefore said to them, “When you have lifted up the Son of Man, then you will know that I am he, and I do nothing of myself, but as my Father taught me, I say these things.
John 8:28 World English Bible
In John chapter 31, we read an account where our Lord told the multitudes after his triumphal entry into Jerusalem that if he was "lifted up" from the earth, he would draw all people to himself (John 12:32). Verse 33 explains that our Lord said this to signify the kind of death he would die, i.e. by crucifixion.
31 Now is the judgement of this world. Now the prince of this world will be cast out. 32 And I, if I am lifted up from the earth, will draw all people to myself.” 33 But he said this, signifying by what kind of death he should die.
34 The multitude answered him, “We have heard out of the law that the Christ remains forever.✡ How do you say, ‘The Son of Man must be lifted up?’ Who is this Son of Man?”
John 12:31 - 34 World English Bible
Today many Christians think that the expression "lifted up" means to praise the Lord Iesus, to lift up his name and to glorify him, particularly during congregational worship in Church on Sunday morning. Eight years ago, I wrote my thoughts and observations on this misconception, link below:
