how to delete 100 pictures from one drive at one time i can delete one at a time but how to select all at once an delete all of them how do I do it?
You can use the OneDrive app for Windows Phone to select (there's a button in the app bar) multiple images and then delete them. Unfortunately there is no option to select all items, but you could just delete the folder.
Or you can log in to your account on OneDrive.com and delete the images from there.
To quickly mass-delete ALL photos at once, select "Files" (not "Pictures"). This will bring up all of your various folders. Select "Photos" and hit the "Delete" button. You can then select whatever other Folders you may want to delete the contents of as well. Then go back to the main page and "Empty Trash Folder". Now you can also see how much space you have in your Onedrive. Again, doing this wipes out everything in that File Folder.