Pictures saved to the iPad's Photos app either by taking the picture, a screenshot, or importing/saving it localy are fairly easy to save to the computer. The quickest way is to use the USB to lightning cable that came with your iPad to connect it to the computer. On a Windows computer the iPad should show up as a USB drive. The pictaures will show up in the DCIM folder or subfolder. On a Mac you can use the Image Capture untility to view and download the pictures.
In both cases it is a bad idea to delete the pictures from the iPad using the computer. Do your deleting, if any, locally on the iPad to avoid damaging the Photos app's database.
There are numerous apps that will let you copy pictures from your iPad to the computer if they are on the same wi-fi network. The one I use is PhotoSync by touchbyte. There is a free companion app you can use on the computer, but it isn't necessary.