Transferring mons with PkHex / PKSM from any gen to any gen?

[javipro_04]

I'd like to know what's the best way to transfer my Pkm (I have VC Gen1-2 legit .cias, Gen3 .GBA roms converted into .cias, Gen4-5 .nds roms and Gen6-7 .3ds converted into .cias // that's the best way or can and should play them in .3ds?) from any gen to any gen using PkHex (or maybe Pksm?). Any uselful guide explaining how to do it? Thanks.

[theSLAYER]

PKHeX.

Use it to open the save, and import the mons into whatever game you're importing into, as long as you're doing it between Gen 1 to Gen 7.

Do note that legal transfer limits apply, if you want the mon to be legal.
If not, just transfer away illegally.