To open this, you must have all subsequent files (e.g., Wedding Pictures.7z.002 , Wedding Pictures.7z.003 , etc.) in the same folder as Wedding Pictures.7z.001 [7-Zip FAQ]. How to open it:
Splitting files is a common technique to bypass file size limitations on cloud storage, file-sharing sites, or email attachments.
You cannot extract the photos from just the .001 file alone; you need the entire set. If you are having trouble opening it, I can help you with:
Download (Windows) or an equivalent tool like The Unarchiver (Mac). Place all files ( .001 , .002 , etc.) in a single directory.