How can I get more GB to my iPad?

If your internal storage is full, your only option is to better manage the storage that you have - and delete unused Apps or unneeded data. The internal hardware and storage is not upgradable - and is fixed for the entire lifespan of the device.

These support pages may prove to be useful:

What's the difference between device storage and iCloud storage? – Apple Support

Manage your iCloud storage – Apple Support

How to check the storage on your iPhone, iPad and iPod touch – Apple Support

Clear Other storage on your iPhone or iPad - Apple Support

External storage devices may be helpful for offloading data to which you do not require regular access - however, for the most part, this data cannot be directly accessed/viewed/edited/manipulated unless it is first copied back to the iPad. Despite optimistic marketing by Apple, iPad cannot replicate much of the flexibility of a traditional computer such as you may be attempting to make comparison.

Should you decide to investigate external USB Storage options you’ll require an Apple Lightning to USB3 Camera Adapter:

https://store.apple.com/uk/xc/product/MK0W2ZM/A

To provide sufficient power for the USB drive, you’ll need to connect a Power Adapter (charger) rated at least 12W to the auxiliary Lightning port of the Camera Adapter. The iPad, on its own, except for very low power devices, cannot supply adequate power for connected USB storage devices. The Power Adapter supplied with your iPad, with the appropriate cable, is likely to be adequate.

In all cases, your USB storage must have a single data partition - and be formatted as FAT32, exFAT, APFS or HFS+. iPad cannot read multi-partition devices, or proprietary device formats (such as NTFS).

I hope this insight and information proves to be helpful to you - if only in promoting some additional though as to your needs. If you have further questions, please don’t hesitate to ask.

You don’t.

Apple iOS/iPadOS devices have fixed internal storage that can never, ever be increased/expanded.

If you need to free up free data storage space on an iPad/iDevice, you need to start by backing up your iPad to either Apple's iCloud ( you may need to pay for additional, monthly storage space ) or by connecting your iDevice to a computer running the latest iTunes or, if a newer Mac with a much newer macOS, use the macOS Finder to do the device backup and/or some other offsite, “cloud” data storage/backup services, like Google Drive/Photos, BOX, DropBox, Amazon Cloud Drive, Flickr ( for photos/images ), etc.

Then, delete any installed apps that you no longer use or use infrequently enough that they aren't missed (you can always reinstalled any purchased or free apps at some time later, as you need them).

In addition, uninstall any games that appear to be using a sizable chunk of your iPad's internal storage, as well!

Then, thin out/delete any music/videos/movies/TV shows/podcasts/screen recordings/images/eBooks/

eMagazine/iBooks/audio books/Documents/PDFs, etc.

If you use a POP email account on your iPad, delete/thin out any old saved emails that maybe saved to your iPad.

To permanently delete photos/images off of your iDevice go into the Photos app and find the Recently Deleted folder/album and permanently delete any photos/images stored in that folder/album.

Also, you can check to see what other stuff is eating up all your valuable data storage space by going into the Settings App,,General Settings Panel, in the right hand column, tap Storage & iCloud usage panel ( in iOS 11 and later, it’s now called iPad Storage ), in the top Storage Panel, tap the Manage Storage panel, wait for a list of apps to generate that will tell you how much space each app is taking up on your iDevice.

Then, for older iPads or iPads with a Lightning connector, do a hard reset of your iPad by holding down both the Home and sleep/wake buttons simultaneously until your iPad goes to black and restarts with Apple logo, then release the buttons.

iOS devices and iOS/iPadOS need to maintain, at the very least, a minimum of between 2-4 GBs of free data storage space, AT ALL TIMES, to insure normal/nominal functionalities/operation and general overall performance of any iOS device running iOS/iPadOS.

Sorry & Good Luck to You!

You can not add storage space to an iPad.