If your device is Activation Locked, this help page will provide most of the information that you’ll need:
https://support.apple.com/en-us/HT201365
If you have forgotten your AppleID or associated password, these can be recovered here:
https://iforgot.apple.com
To recover your credentials, you’ll need access to one of the following:
- Your primary email address mailbox that corresponds with your AppleID
- Any of the secondary/recovery email addresses that should be configured for your AppleID account
- Any of the trusted telephone numbers (fixed line or Cellular/Mobile) that are associated with your AppleID
Unless you AppleID account has not been fully/correctly configured, or has been seriously neglected, recovery of the AppleID and password should not be difficult.
More information about recovery of your AppleID:
https://support.apple.com/en-us/HT201354
More information about recovery of your AppleID password:
https://support.apple.com/en-us/HT201487
When you recover access to your credentials, you would be well advised to log-in to your AppleID account from a web browser - and verify/update any email addresses and trusted telephone numbers:
https://appleid.apple.com
All this said, resurrection of your original 1st Generation iPad mini might be a futile exercise. Update Support for the iPad mini1 was formally ended by Apple in September 2016. The final supported versions of iOS were iOS 9.3.5 (WiFi Only models) and iOS 9.3.6 (WiFi & Cellular). iPad mini1, a 32-bit device, cannot be updated to any newer major versions of iOS as they lack the required minimum hardware specifications.
Many App Developers have also dropped support for older devices and iOS versions preceding iOS11/12 - and have withdrawn older versions of their Apps from the Apple App Store. As such, with scarcity of compatible Apps, in particular for 32-bit devices (64-bit now being the only supported standard), utility and usefulness of older iOS devices is becoming increasing limited.
If Apps that you need to use now have higher minimum iOS-version requirements, your only option is to replace your iPad with newer model. Even the basic current iPad model supports current iPadOS 13.x - and has hardware specifications that will vastly outperform your old iPad.
Sorry, this is clearly not the news that you were hoping to hear.
I hope this information is helpful - if only in clearly stating your current options and potential ways forward.