I want iOS 14 on my iPad

The tags appended to your post suggest that you have an iPad Pro. All models of iPad Pro can be updated to the most recent version of iPadOS - at this time, iPadOS 16.5.1(a).

All iOS/iPadOS updates are cumulative. You can only update to the most recent version; intermediate versions are not available.

If your iPad is capable of update to a more recent version of iOS/iPadOS than is currently installed, these support pages outline both the available methods by which the update can be performed - and troubleshooting should you experience difficulties:

Update your iPhone, iPad or iPod touch – Apple Support

If you can't update or restore your iPhone, iPad or iPod touch – Apple Support

If your iPhone, iPad or iPod touch won’t update - Apple Support

iOS update and restore errors – Apple Support

Be aware that while an iPad may be capable of update, in some circumstances (such as being two or more major versions behind the current release) you may need to use a computer to perform the update. To do so, you will need access to either a Windows PC (with iTunes for Windows installed) or a Mac (with iTunes or Finder - as appropriate for the installed version of macOS). Ensure that your installed version of iTunes has been updated to the most recent version; the essential device drivers are included.

Download and use iTunes for Windows – Apple Support

Update to the latest version of iTunes – Apple Support

Update software on iPhone, iPad or iPod touch in iTunes on PC - Apple Support

If you have a beta profile installed, ensure this has been removed from your iPad - as, otherwise, installation of production software updates may be inhibited. This support page provides the necessary information to remove the beta from your iPad:

How to uninstall iOS beta software - Apple Support

You should note that for your iPad to install an available update, its battery must be charged to at least 50% capacity - and/or be connected to its Power Adapter. Similarly, the iPad can only be updated over a standard WiFi connection - or be updated by a PC or Mac using iTunes or Finder - over a USB connection.

If you have an iPad Pro (6th generation) as suggested

by the tag in your post, it is compatible with iPadOS 16

and will not install iPadOS 14 as that is no longer signed

by Apple.

iPad models compatible with iPadOS 16 - Apple Support

If you own an iPad Pro, there is no way to get iPadOS 14, at this very late date.

The ONLY OS you can upgrade your iPad Pro to is the latest iPadOS 16.5.1.