ARC file is a compressed archive file format designed by System Enhancement Associated (SEA). Compression reduces the size of the archive containing one or more files or folders to facilitate sharing of files with other users.
After converting the file to the new format, you will be able to use other programs to support it. Keep in mind, however, that the UPF file after converting to ARC may differ slightly from the original. The most important information should be kept, but if you want the file after conversion from UPF to ARC to be the same, you have to do this carefully and choose the proper application from the list below.
There is no guarantee, of course, that the conversion will come up to all your expectations, but it will certainly help you. If, after all, the effect of converting UPF to ARC does not meet your expectations, you can simply try to find on the Internet a different version of your file in UPF format, properly converted to a ARC file by someone else. If this fails, use the information provided in the further part of the website.
Unfortunately, if after performing the two previously described steps (trying to find your UPF file converted by someone else, and the attempt to convert it to ARC on your own) you still have a problem with your file, then there are only a few solutions left. You can once again try to find and install an application that can open the UPF file in its original format (without conversion to ARC file). Such a solution will be difficult to implement, but it certainly will give the best result.