How can I move videos from Google Drive to Apple Photos on iPad?
From this Google article:


  Open the Google Drive app.
  
  Next to the file you want to download, tap More.
  
  Tap Send a copy.
  
  Depending on your file, tap Save image or Save video.


If you want to save multiple at once you will need to move the files to Google Photos and have them in a folder.

Then:


  On your iPhone or iPad, open the Google Drive app.
  
  Tap Menu and then Settings.
  
  Under Google Photos, turn on Auto Add. At the top, tap Back.
  
  Find and open the Google Photos folder.
  
  Select the folder you want to download.
  
  Tap More and then  Select All and then Download.