Open the Google app on your iPhone
Tap your profile picture in the top right
Tap Search history
Tap Delete
Choose a time range or select All time
Confirm by tapping Delete
To clear Chrome history, open Chrome on your iPhone
Tap the three dots at the bottom right
Tap History
Tap Clear Browsing Data
Select Browsing History
Choose the time range
Tap Clear Browsing Data
Confirm by tapping Clear Browsing Data
To clear Safari history, open Settings on your iPhone
Tap Safari
Tap Clear History and Website Data
Confirm by tapping Clear History and Data