I lost all my pictures

That depends on how you saved them or backed them up. Here are some of the ways you might have; do any ring a bell?

• Backup your phone to iTunes; just restore your phone from the backup
• Backup your phone to iCloud: Likewise
• Sync your photos to iCloud (NOT the same as backing up) -Settings/<your name>/iCloud - Photos-ON
• Copy them to your computer using iTunes (NOT the same as backing up) -->Keep your photos safely stored and up to date on all of your devices - Apple Support
• Stream them to your computer when taken using Photo Stream -->About iCloud Photos and My Photo Stream - Apple Support
• Archive your photos with a 3rd party service such as Google Photos, Upthere.com, Shutterfly, etc.

If you didn't do any of these things you cannot recover your pictures

Watch the video to know how to use Photos.

Hi,

Thanks a lot for posting your question on Apple support community.

To get support please specify if you have taken any backup on iTunes or iCloud.