Hi,
I'd appreciate it if you anyone could help me write this address in a formal letter. A factory is located 5 Km away from the city A. (It's next to the motorway from the city A to the city B)
Thanks in advance.
Here, remote places like that usually have a PO BOX or a special address that you can find by contacting them. I wouldn't just write "go 5 km to the left, turn right, go straight for 200 meters.... etc".
If you are having a fair of some sort and you want people to find it, you could give them directions to the location of the fair. What you have provided is not an address, they are directions. Directions usually work fine for these sort of affairs. Write something like, "Go five miles south of City A on highway #14. Look for signs for the fair."