A file ending in .001 is a "split" volume. It cannot be opened by itself because it only contains a fraction of the total data.
: Use a tool like Keka or The Unarchiver . native_plants_of_australia.7z.001
: Ensure all parts have the exact same name except for the trailing numbers. 2. Extract the Content A file ending in
: Double-click the .001 file; the software will automatically join the subsequent parts. How to Extract .7z.001 files - Microsoft Q&A native_plants_of_australia.7z.001