Ensure "Back up & sync" is turned on in the app settings. You can then visit photos.google.com on your computer to view and download your images.
If your iPhone photos end in .HEIC and won't open on your PC, go to Settings > Photos and select "Automatic" under "Transfer to Mac or PC" to ensure they convert to standard JPEGs when moving them. How Do I Pictures From My Phone
Windows users can use the Phone Link app to wirelessly view and copy the most recent photos from an Android device. Ensure "Back up & sync" is turned on in the app settings
The fastest and most reliable way to move large numbers of photos is with a physical cable. How Do I Pictures From My Phone