Ensure you have .part1.rar , .part2.rar , and .part3.rar .
Knowing this helps me tell you exactly what software to use to open it. SD Card 256mb.part3.rar
Use WinRAR or 7-Zip to open the first file (part1). Ensure you have
Based on the file naming convention, is a segment of a multi-part RAR archive . Ensure you have .part1.rar
The .part3.rar extension confirms this is the third piece. It cannot be extracted alone.
Typically used for transferring files larger than what a single email, file-hosting service, or storage medium (like a small 256MB SD card) can hold at once.