I bought more iCloud storage yesterday, when does it get put onto my iPad? Need to update and need storage to do it.

i cloud storage does not add to your ipads local storage

read

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

If you bought that extra iCloud storage just to update your iPad, it doesn't change the situation (perhaps it is a problem related to your iPad internal storage, and there's no way to increase that storage, except deleting some unused stuff).

If you bought it to have more space to backup your iPad content to iCloud, then it's okay, but it might take a couple of days to get it.

Regards

Giulio