You only need to right-click and extract ex01.part1.rar . Your extraction software will automatically detect and "stitch" together the data from all other numbered parts in the sequence.
To properly access the contents of this archive, follow these steps: ex01.part1.rar
If any part of the sequence is missing, the extraction will fail, as every volume is required to rebuild the original file. You only need to right-click and extract ex01