I think he was asking for the step by step, so I will try to answer his question again:
Search in your save folder for a file called MAJORA'S MASK-*SOMERANDOMNUMBERS*.EXTENSION and export to any folder you like... then create a new save with your "new" Majoras Mask Rom, save and search for the newly created MAJORA'S MASK-*SOMEOTHERRANDOMNUMBERS*.EXTENSION save file... copy the full name, delete it and import your old save file back to the save folder and rename it to your newly created save file!
That's it... and next time, please do not create multiple threads for the same question!