Determine distance from the galactic center in DS9
You cannot estimate the distance to anything or from anything in 3-dimensional space using a 2-dimensional coordinate alone.

You may calculate an angular distance (as per Mike G's answer), then assume they are all at a common distance and translate that angular distance into a physical distance, but since they aren't all at the same distance, that won't work.

To do what you want requires an estimate of the distance to these sources.