Hi, and welcome to this Apple (user-to-user) Community!
Re: "How can i get the amount originally on my Apple Gift Cards?"
Am no expert in this area, yet your post to the community deserves some response.
To view the amounts: See if you can locate the original receipts from Apple (maybe search for receipts emailed to you ... or you may have paper receipts filed somewhere ?). Seems there is no history of redeemed gift cards.
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Re: "My husband has dementia and we purchased some gift cards for our grandchildren for different occasions.
I recently found a stack and some are scratched off but i don’t know which ones had what amount because i didnt have them all on my apple account. "
You may want to check online for the balance of any gift card that has already been redeemed to your own account See how to: Check your gift card balance - Apple Support
Else: You may need to redeem a card in order to get the amount.
To find out how to redeem each gift card(s) and what you can buy with it, check which type of gift card you have.
What type of gift card do I have? - Apple Support
The amount from redeemed App Store or iTunes cards gets added to your Apple Account balance to be used for Apple media purchases: Eg: What you can buy with your Apple Gift Card or Apple Account balance - Apple Support
(NB: Seems you can not use a Gift card balance for more gift cards though)
If needed:
More info: How to redeem your Apple Gift Card, App Store Card, or App Store & iTunes Gift Card - Apple Support
& What to do:
If you can't redeem your Apple Gift Card, App Store Card, or App Store & iTunes Gift Card - Apple Support
Hope there's something helpful to you here.
All the best :-)