just so you know when you go back to the store you got the cable from.
First, they will take it back if you have the bill or the plastic it came in.
ide cables: if it fits on a hard drive or cdrom or cd burner or dvd burner, then it would be an ide cable.
The standard is, i think, 18 in and has 2 connectors plus the connector that goes to the motherboard.
Sometimes you see ide cables with only 1 connector besides the one that goes to the mobo. And you see ide cables in sizes from 12 in, 18 in, 24 in, and even 30 and i believe also 36 in. Use the smallest you can use in your setup.
You have to bear in mind that when you connect an ide cable to the mobo and then to 2 devices, say a hard drive and then to a cdrom, usually you have to twist the cable at some point so it goes on correctly on the second drive, so you have to figure all that when you are figuring out what size to get. If in doubt between the 18in and the 24in, it wont do any hard to get the 24in, or try the 18in and it its too small, bring it back and get the 24in. Only use 30in or above if you absolutely have to, like in a full tower maybe, but for a standard tower 18in to 24in will do fine.
On the package it should state eith ide or ata (same cable, just different words), and also it should state the length of the cable.
The one you have, if there is a package it came in, it likely says "scsi" on it somewhere? But if it wont fit on a hard drive or cdrom drive, then its likely a scsi or even a floppy drive cable. Some floppy drive cables can be very long.