Welcome to Android Central! Were all of the photos saved to the phone's Internal Storage or the microSD card? Have you used the My Files app to look at the /DCIM/Camera directory (or any other directory where you may have saved photos) to see if the files are still there? Or connect the phone to your computer via USB and use Windows Explorer to look.
In the future, I would strongly suggest using Google Photos Auto Backup, or something similar. Either that, or make it a habit to backup your photos to your computer or to some other cloud storage on a regular basis.