I bought two Playstation cards to add to my Playstation store wallet, but every time I try to add the funds, it says to me that the number its wrong or invalid.
After that, I knew that my account is a Saudi Arabian account, and the card that I bought one of them through online, and the other is from Future Shop in Canada.
Can anyone help me out if there is any other way to exchange/use the card with a Saudi account?
It's possible you're not able to use them (as far as I know they're kinda "region locked"). Your best bet would be asking Sony's support, as these guys will be able to give you the 100% correct answer and they might even be able to exchange your keys or add them manually if you're lucky.
As Mario said, your best bet is to contact Sony.
Your second resource is to talk with the person who sold you the wallet cards. Ask him if you can exchange the cards for cards that work with a SA account.
