Your perfect Pack ‘n Play needs an ideal sheet. Not a crib sheet, but a sheet meant explicitly for a Playard. Check up what to consider when buying a Pack ‘n Play sheet.
pack n play
You have a crib and lots of cute fitted sheets. Does their size also fit your Pack ‘n Play mattress? In rare cases, this is possible. But more likely, the interior dimensions of your crib and Pack ‘n Play are not the same, meaning you will need sheets of different sizes.