Ok, so that's an Android.
As long as either 1) Your old phone's pics were all in the main Gallery, or 2) Your old phone's pics were in multiple Albums within the gallery, but all those were included in the Google Photos app's Backup & Synch settings, they should all be on Google photos. After that point if I go to photos.google.com and sign in, all my pictures are there (albeit a big disorganized). From there you can easily click the upper right menu area to download 1 specific picture, or multi-select pictures and then download a Zip of all of them. If you're sure that all your pictures aren't there (online), then I would see if you can recover/power up your old phone and go through that backup/synch process again, making sure first to go into the Photos app's Backup & Synch settings and ensure that your entire Gallery, and any folders you wish to backup photos from, is selected/included. That's all I can think of .... good luck and hope you find them soon!