A three way to a one way??

Hi, we a remodeling our old bathroom and the current shower/tub has a three way faucet. We would like to go to one of those newer one way handles. The manifold just screws in soooo.... can we just find the corrosponding parts, pipe, and just keep screwing them in until we get enough to connect the new manifold?

Very unlikely that you could find enough adapters to make this work. It would certainly be a Rube Goldberg.

Get a plumber to properly solder in the new valve.