forget the adobe ID where we registered our CS6 Serial.

"we have the original Packaging with the serials..."

In that case, you don't need a log-in. 

CS4, CS5 and CS6 are on life support. But they can still be activated providing you have the following:
1. original media (disks or downloads) you received at purchase and a way to read them,
2. a legitimate serial number for that version, language and platform (Win/Mac),
3. an older operating system that can support legacy 32-bit apps.
--------------------------
NOTE 1 : Creative Suite installers won't work on macOS Sierra, High Sierra or Mojave without terminal workarounds. See the help article below.
https://helpx.adobe.com/creative-cloud/kb/install-creative-suite-mac-os-sierra.html

NOTE 2: Creative Suite cannot run on Catalina. Either downgrade your OS, set-up a virtual machine or get all new, 64-bit software. Your choice. https://www.adobe.com/creativecloud/plans.html

NOTE 3: Legacy Creative Suite is discontinued & unsupported. Use at your own risk.

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Beware of fake Adobe reps who may contact you privately offering to sell you software or take control of your computer. It's a scam, run away!  Real Adobe employees will never reach out by Outlook, Gmail, Hotmail or Skype.
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3 Easy Ways to Identify Genuine Adobe Staff
https://tinyurl.com/10791730

We are volunteers and users, just like you. We cannot help with account and/or payment problems/questions — only Adobe Customer Service can do that. 

All we can do is to give you the correct information. 

Contact Adobe Customer Care: https://helpx.adobe.com/contact.html 

Click the chat icon in the lower right and type "agent" to get a human and not the chat bot.