I'd recommend installing the Google Photos app on your Pixel phone, it includes a handy and automatic backup & sync function so the entire photo library on your phone gets uploaded into your online Google account wirelessly. If you have a lot of photos the initial upload could take a while but once done you'll at least have a fully accessible backup, which it sounds like you don't currently have. Be sure to go into the app's Settings menu and set it up properly -- in the Back up & sync menu under 'Upload Size' choose the 'Original' option instead of 'High quality' (the former uploads your photos at their full resolution, the latter scales them down to save on storage space); and enable the 'Google Drive' option, linking the Google Photos and Google Drive services so you can then access your entire photo library on your PC using a web browser. You can go to
https://photos.google.com
and access your photos through the Google Photos web interface or
https://drive.google.com
and access your photos directly as actual files.