Open the Photos app
Select the image you want to search
Tap the Info button if available
Use Visual Look Up if it appears
Tap Search or Look Up results shown on the image
Open Safari or Google Photos if you want to search the image online
Go to images.google.com in Safari
Tap the camera or upload icon
Choose the photo from your iPhone
Review the search results
Use the Google app and tap the Lens icon
Select the image from your Photos library
Check the matching or similar images shown
Use the Files app if the image is stored there
Share the image to a search app if needed