I'm sure these kinds of questions are asked all the time but is it possible to mount an old SLR lens like this on a newer DLSR camera? The Tokina lens is made for a Pentax K1000 and I have a Nikon D3300. I've also got a Canon FD 70-210mm zoom lens but I read online you can't use those with DSLR bodies. Does anybody know where I could find an adapter for these lenses, if they're even compatible? Any info would be appreciated.
It is not possible. Adapting lenses is all about the flange distance. An adapter can make the distance longer but not shorter, unless it has some quality-reducing optics are used which is quite rare and expensive.
The flange distance of the Nikon F-mount is longer than both Pentax K-mount and the Canon one, so there is no adapter that works that way.