Why are my pictures not on my iCloud?

Do you have iCloud Photos turned on in your device?

If you have iCloud Photos turned on, the photos on the device are the same as on iCloud, with the possible exception that some of them may be space-saving optimized versions if you have that option turned on. You view them in the Photos app on an iOS device or Mac. You can also login to icloud.com and go to the Photos app there. The following Apple article has information about iCloud Photos: Set up and use iCloud Photos - Apple Support

If you didn't have iCloud Photos turned on but do have an iCloud backup, you can restore the entire phone (not just the photos) from iCloud but you cannot otherwise view the contents of the backup. The following Apple article has information about backup: Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

If they are in Recently Deleted on your device or at iCloud.com (normally only there for 30 to 40 days). See: If you're missing photos or videos in the Photos app - Apple Support