How can i save my important photos to my Apple id if it is only on that device?

Starting with some basic understanding of iCloud and your Photo Library...

The default location for Videos and Photos to be saved on your iPad is within the iPad's Photo Library.

While you can enable iCloud Photos to (a) synchronise your Library between Apple devices and (b) access your Photo Library from any computer using a web browser - using iCloud Photos does not provide the ability to keep your photos/videos just in iCloud. You must understand that deleting items from your Photo Library will cause the corresponding copy to also be deleted from iCloud Photos. As such, iCloud Photos is not suitable for use as a independent repository for your photos and videos.

While iCloud Photos is not, of itself, suitable for maintaining a device-independent location to store your photos/videos, you can still use your available iCloud storage to save your media. To do so, you will need to export your photos/videos from your Photo Library to a folder that you create in your iCloud file storage...

Using the native Files App, create a folder in iCloud - within which you will initially save a copy of your selected photos and videos.

Next, open your Photos App - and from your Library, tap to select the items that you wish to copy to iCloud file storage. When you have selected the items that you wish to copy, tap the Share button (a square with an upward-pointing arrow) at bottom-left of the Library window.

Tapping the Share button will expose an action menu; from the menu select Save to Files - and navigate to the iCloud folder that you have created - then tap Save. Your selected photos/videos will be copied to the folder that you have selected.

Don't try to copy all your photos/videos in one go - as this will be very slow and may fail due to insufficient system resources. Instead, copy across small batches.

When you have finished, check that all your photos are visible using the Files App. You should note that photos and videos that are not stored within the Photo Library cannot be accessed or viewed using the Photos App.

When you are happy that you have copied your photos/videos to the intended folder, only then is it safe to delete the original image files from your Photo Library.

This technique can be used to save your Photos to other forms of storage - such as other Cloud storage services (e.g., Microsoft OneDrive, Google Drive, Box - some of which offer free storage plans) and USB storage devices that you connect directly to your iPad.

Connect external storage devices to iPad - Apple Support

To be clear, while you can save copies of your files and photos to a Windows PC or Mac computer if you wish to do so, you are not reliant upon these options.

You can copy your photos to your computer, for example.

Have a look at this article:

Transfer photos and videos from your iPhone or iPad to your Mac or PC - Apple Support

Remember, that iCloud Photos does not back up your photos. If you delete or modify photos on your iPad, the changes will also be made in iCloud.

However, if you already synced your photos to iCloud, you can copy these files to your computer as well:

Archive or make copies of the information you store in iCloud - Apple Support