Yes 1mg is roughly equivalent to 3mg of Ativan. . . You CAN crossover directly to the klonopin if you wish, but I'd probably suggest doing it in stages. . . . Just to be on the safe side. It wouldn't take very long. . . I did something similar to this when crossing from ativan to valium.
For example if you take 2 daily doses of ativan (you didn't specify, but should be able to figure it out on your own.) A=Ativan . . K= Klonopin
Day 1| Dose 1) .75mg A + .25mg K Dose 2) 1.5mg A
Day 2| Same as day 1
Day 3| Dose 1) .5mg K Dose 2) 1.5mg A
Day 4| Same as day 3
Day 5| Dose 1) .5mg K Dose 2) .75mg A + .25mg K
Day 6| Same as day 5
Day 7| Two doses of .5mg Klonopin, 0 Ativan.
Essentially you are just doing it in stages, changing one dose at a time, and just taking half the amount in ativan, half in klonopin, before switching that dose completely over to Klonopin. You don't HAVE to do it this way, you can directly crossover if you so choose, probably without issue. But if you run into issues, follow my outline and you'll be fine.