Can I convert a midi in 3/4 to 4/4? Sort of a multiple copy+paste

I have a midi file in 3/4. I need to convert it to a 4/4.
For much of it, it would make sense musically to "copy" every third beat and "paste" it as the fourth.
I can do it in Piano Roll: Select All events, deselect the first three measures, move all a beat right, repeat. I'be tried it with 12 bars and I find it'll work, but it's awfully tedious. Does anyone have a more efficient, automated suggestion?
Thanks.