Hello Chandrasurya,
Thank you for your post. .arj extensions are compressed filetypes similar to .zip extensions. This filetype will require you to get a 3rd party software in order to work with these files. You can perform a web search on Bing.com or your favorite search engine for ".arj extractor" in order to find the software you need. Please let us know if we can assist you further.
Cheers