I am in the process of remodeling a garage conversion done by the previous owner.
To properly cover up the stem wall, I used notched 2x6 framing over the existing framing.

All the framing seems secure, but I'm wondering if i still need to attach the sole plate to the concrete floor. Appreciate any info.

What's a "stem wall"?

Imagine a concrete base moulding that extends 8 inches vertically and 3 inches horizontally along the perimetr of the wall. Is "stem wall" the correct term?

Never heard the term before...back to your original question...I assume the 2x6's are notched 3 inches, so that the sole plate is approximately 2 1/2 inches wide, and the bottom of the studs, which actually bear on the top of the concrete foundation, extend down over the concrete to the sole plate. If possible, I would anchor the sole plate here and there...maybe every 4 feet or so,

That's correct, the sole plate is pressure treated 2x4. What's the best way to anchor them?? Thanx much for the info.

The anchorage isn't critical. Use nails that are designed to go into concrete. One every four feet should be adequate...all you want to do is prevent minor movement of the sole plate.

Thanks again.