I bought lightroom5 on Amazon. i need the serial # to be able to use it but i have no way of getting the serial number. i read i can get it from on the DVD case it came in, on the receipt, or in the confirmation e-mail but i don't have any of these. is there any other way to get it. like tracking when i bought it and maybe having the serial number on file???
If you did register with Adobe user your AdobeID and find the serial in your account.
If you have it installed, you can find it in the registration file: https://helpx.adobe.com/lightroom/kb/preference-file-locations-lightroom-41.html
Otherwise, you're out of luck.
You bought it from Amazon as a Boxed Version, IE It came in a Box? Or as a Download? If it originally came in a Box what did you do with the Box? If it came as a download they sent you an email with the serial number.
If you lost either the box it came in or the email they sent you, and you didn't register it under your Adobe ID account (And you never bothered to make a copy of the serial number) you will need to buy LR again. There is no other way of obtaining the serial number.