Parameter is Incorrect -- HELP!

I have a Seagate external hard drive that's not working and all my files are on this drive. I keep getting 1 of 2 messages. One is either "you need to format the disk in drive H: before you can use it. Do you want to format it?" I believe if I format it, it will erase all my data and I definitely don't want that to happen! The other message I sometimes get is "H: is not accessible. The parameter is incorrect". I don't know what that means but it only allows me to click okay. I tried the USB 3.0 Universal Drive Adapter to make sure the hard drive was working. The motor is running and the adapter is showing the blue light which I believe means that's working. What else can I do or how do I fix the incorrect parameters?