You must have all parts of the split archive ( .001 , .002 , .003 , etc.) in the same folder to decompress the data [7-Zip Documentation].

Right-click the first file ( .001 ) and select 7-Zip > Extract Here or Extract to... . The software will automatically merge the files and extract the contents [7-Zip Documentation].

Keep all parts together when transferring files to prevent losing one, which makes the set useless.