I accidentally uninstallated Keynote, Numbers & Pages from my iPod Touch

Hey! Good afternoon,

I've got a problem:

When I first had my iPod Touch I used to have Keynote, Numbers & Pages, but I don't know why & how I uninstalled them; I really need the apps, y'know, for school works & all of that, but I don't have them, & I have to pay for them now, I don't have an App Store Card right now,but I was thinking, "If I uninstalled them, they must've been stored in the downloads space, right? I'm just gonna download them again" but, they're not, and I can't. I also tried to download them in my laptop, and then pass them to the iPod, but I couldn't pass them.

Do you know how can I install them back without paying?

Beforehand, thanks