The centre of gravity is the located at the point where it will balance level supported on either a proper CG jig, or usually your fingers!
Put one finger under each wing, the same place each side, nearest the fuz, not the wingtips, and pick up your plane with the two fingers.
Usually CG is about 1/3 back from the leading edge.
When you find the point when you pick up the plane by two fingers where it balances level, thats where the centre of gravity is.
Move your fingers fore and aft a little at a time till you find it.

Personally, I wouldn't bother messing about going from a taildragger to a trike, it's too much messing about, plus the steerable nose gear will end up letting you down at some point, most experienced flyers do away with them from the beginning and fix the wheel straight.
Most flyers convert trikes to taildraggers if anything, not taildraggers to trikes.

Hope this helps.