You can move a question from one Form to another Form. Go to Workflow > Edit Forms, and select Edit by the Form containing the question(s) you want to move. Select the question(s) by clicking the checkbox in the Bulk column.
Then, select "Move to Form" from the Bulk Actions. You will be prompted to select the Form to which the question will be moved.
Note: moving a question removes the question from its current Form. If you have data submitted for that question on the original Form, that data will no longer be available.
Visit the Form Editor page in the User Guide for additional information.