How do you redeem Sims 2 disc code on Origin?

So I have a disc copy of The Sims 2. I want to switch my disc onto Origin, just so it's there whenever I want it, and so I don't have to put discs in, etc. I've already tried redeeming the product code on Origin, and it tells me it is an invalid code. Live chat support tells me to reach out to the place where it was purchased from. The problem there is, the game was gifted to me and was bought in 2007. I need some proof of purchase, however, there is none as it was bought close to 15 years ago. What should I do?