Here "be turned" is a metaphor for a person repenting and worshiping the Lord. This can be stated in active form. AT: "He will cause many of the people of Israel to repent and worship the Lord their God" (See: [[rc://en/ta/man/translate/figs-metaphor]] and [[rc://en/ta/man/translate/figs-activepassive]])
Here "the face of" someone can be an idiom that refers to the that person's presence. It is sometimes omitted in translation. AT: "the Lord" (See: [[rc://en/ta/man/translate/figs-idiom]])
"with the same spirit and power that Elijah had." The word "spirit" either refers to God's Holy Spirit or to Elijah's attitude or way of thinking. Make sure that the word "spirit" does not mean ghost or evil spirit.
The heart is spoken of as if it is something that can be turned to go in a different direction. This refers to changing someone's attitude toward something. (See: [[rc://en/ta/man/translate/figs-metaphor]])
What the people will be prepared to do can be stated clearly. AT: "make ready for the Lord a people who are prepared to believe his message" (See: [[rc://en/ta/man/translate/figs-explicit]])