Hi Anna! Jen Bokoff from Foundation Center's Knowledge Services/GrantCraft team here! Thanks for thinking of Foundation Center; I want to just clarify that we can do for you.
We can indeed accept all data and can process it, though historical data before 2006 won't show up in our regular subscription products, but would be available for custom apps and APIs. There would be a fee depending on how far back the data goes and what your goals are, but we absolutely can help! feel free to shoot me an email (email@example.com) and I'll make sure the right person gets back to you.