What is the correct indirect speech for: "He said, 'He will go to Karachi next week.'"

He said that he will go to Karachi next week.

He said that he would go to Karachi the following week.

He said that he had gone to Karachi the next week.

He said that he goes to Karachi the following week.

When changing from direct to indirect speech:

"Will" changes to "would".

"Next week" changes to "the following week".