The iPad3 is long-ago obsolete. If the 30-pin dock-connector has been damaged in any way, repair will not be possible.
Apple ended support for these iPad3 in September 2016. The iPad3 cannot be updated beyond iOS 9.3.5/6 as the internal hardware does not meet the minimum technical requirements for newer versions of iOS/iPadOS. This limitation cannot be bypassed.
Be aware that even if you are able to resolve your immediate problem, there are no longer any compatible Apps for the iPad3. App Developers have dropped all support for obsolete 32-bit devices - and many for iOS versions preceding iOS11/12/13. As older versions of Apps have been retired and removed from the Apple App Store, this may severely limit the usefulness and utility of your iPad. As such, if you want or need to access most current Apps, requiring more recent versions of iOS than your iPad is capable, you’ll need to consider replacement of your iPad with a newer or current model.
Of current models, even the entry-level iPad9 has specifications and capabilities that will massively outperform you current iPad - and is compatible with the vast majority of current Apps. Other models are more powerful still.
In summary, you likely have a lost cause.
