Select the rows above and below the hidden rows
Right-click the selected row headers
Click Unhide
Select the rows around the hidden rows
Go to the Home tab
Click Format
Hover over Hide & Unhide
Click Unhide Rows
Select the entire worksheet by clicking the Select All button
Go to the Home tab
Click Format
Hover over Hide & Unhide
Click Unhide Rows
Use the keyboard shortcut Ctrl + Shift + 9
If the rows are hidden by a filter, clear or adjust the filter first