Do you only have an H20?
If so, why convert to swm?
Anyways, you need to go to the receiver to the power inserter, to the power passing port on a swm splitter, to the lnb.
If you just have a H20, then you can remove the splitter.
If the LNB is not powered properly, it will still possibly read a transponder but not the whole set up.
If it is wired right, you need to set the receiver up for SWM3.
Usually a RBR (red button reset) will achieve this.
If not, then you can go in to signal strength and do a repeat satellite set up.