Cues

i wanna know that i'm sure that what i'm downloading a the correct cue file or if it even is a cue file

Cue files are small, only a couple of KB. Generally the file name of the cue file is identical to that of the bin file with the exception of the extenstion.

Correction: they are less than 1 KB big, usually a couple of hundred bytes. ;)

To see if you have downloaded the correct .cue file for the bin, open it with notepad, once you have downloaded it. Check the first line.
It should look something like that:
FILE "Command_and_Conquer_Generals_CD2_Deviance_DonkeyNL_ShareReactor.bin" BINARY

If you have the .bin file, that is named like that, then you have downloaded the correct .cue file.

But as NikkiD said, always look for .cue files that are named exactly the same as .bin files.