It is only the PlayStation game product numbers that, per the Style Guide, requires the dash to be present.
ie: SLUS-20751 and not SLUS 20751
There are not requirements for other item numbers, so they should be on the entry as they appear on the box. If it has dashes, use them, if not then don't.
For Nintendo games that have multiple numbers, if one of them has a country code, then that is the one that should be in the Item Number field.