how do revive a serial code for cs5?

You'll need to get your money back.

One feature of perpetually licensed Student and Teacher Editions such as CS5 is that they cannot be resold so it's unlikely you'll be able to use the serial number even if you manage to retrieve it..

https://helpx.adobe.com/x-productkb/policy-pricing/education-faq.html

Quote from the link above:

"Can I use Student and Teacher Edition products commercially?
Yes, Student and Teacher Edition products can be used commercially on your privately owned computer. They may not be resold."

I suggest following @rayek.elfin's advice and finding an alternative open source or low cost product which will do the job better than the 14 year old CS5.

If I might ask: why would you want to use a very old educational version of CS5? It cannot be used for commercial work. And as a teacher/student such an old version wouldn't be very useful either in my opinion - not with free open source and low-cost commercial alternatives doing as good a job or better.

And where did you find this copy?

You would have to arrange a transfer of license with the current registrant. See https://helpx.adobe.com/x-productkb/policy-pricing/transfer-product-license.html