Using the Find and Replace function

Tap the Tools icon in the right corner of the top toolbar.
Tap the Find and Replace option to open the Find panel at the top of the screen.
Enter your search term in the entry field.
Use the arrow buttons to navigate through the found occurrences towards the beginning of the worksheet (if you tap the icon) or towards the end of the worksheet (if you tap the icon) from the current position.

To refine your search, tap the Search Options icon on the left of the Find panel. The following options are available:

Find — default search mode.
Find and Replace — switches to replace mode (see the next section).
Find and Replace All — replaces all matches at once (see the next section).
Search in — choose where to search: the active Sheet only or the entire Workbook.
Search Areas — choose how the search moves through the data: By row or By column.
Look through — choose what to search inside: cell Values or underlying Formulas.
Match case — turn this on to find only results that match the same letter case as your search term. For example, if you search 'Editor', words like 'editor' or 'EDITOR' won't match.
Match cell — turn this on to find only cells that contain exactly your search term and nothing else. For example, if you search '56', cells with '0.56' or '156' won't match.
Highlight results — turn this on to highlight every match in the worksheet.

Tap the Search Options icon on the left of the Find panel.
Tap Find and Replace. The Find panel will expand to show a second entry field.
Enter your search term in the first field and the replacement text in the second.
Use the arrow buttons to navigate through the matches and tap Replace to replace the currently selected one.
To replace all matches at once, tap the Search Options icon and choose Find and Replace All, then tap Replace All.

To close the Find panel, tap OK button OK in the top left corner.