This will help you write a post that contains all relevant details and is easily answerable by the community. Remember, we're all scientists, not answering robots :)
It would help a lot if you provide more information, like how the files were obtained, what analyses you would like to perform, etc.
But since idat files are Illumina microarray files, you won't get fastq files unless you do some pretty insane magic. Have a look at the BioConductor package illuminaio for parsing idat files.
Please read: A: How do I ask a question on Biostars?
This will help you write a post that contains all relevant details and is easily answerable by the community. Remember, we're all scientists, not answering robots :)