The software will automatically detect the other parts in the folder, stitch them back together, and give you the original file. Is it Safe?
Make sure all numbered volumes of the archive are in the same folder on your computer. jblnqp.7z.001
While the .7z format itself is a safe and widely used compression standard, the inside depend entirely on the source. Always ensure you trust where you downloaded the file from before running any executable files found inside the archive. The software will automatically detect the other parts