I have a square D panel and how can I tell which is the ground bar an which is grounding bar

This can get confusing using the technical terms, but the general way to say it is ground bar and neutral bar.
Is this the main panel (with a main breaker)? If so then usually both bars are shared and serve both purposes.
If a bar is added or screwed to the panel box itself it can only be used as a ground bar.

This can get confusing using the technical terms, but the general way to say it is ground bar and neutral bar.
Is this the main panel (with a main breaker)? If so then usually both bars are shared and serve both purposes.
If a bar is added or screwed to the panel box itself it can only be used as a ground bar.

It is a new panel with a main breaker... the reason I ask is I am adding a 30 amp double pole circuit breaker with number 10 3 wire and I want to make sure I have the ground in the corretc place and the white in the correct place

If your service is from a standard three wire connention at the main paneboard then you will see two black conductors that feed the power bus bars. The third conductor is usually set apart from other two conductors. This conductor will be the Neutral conductor. It connects to the Neutral bus bar. You will see all the white conductors connected to this bar.

There is a third bar, the Ground bar. Here you will find the bare conductors and possibly insulated ground conductors.

In a thumbnail here is how it works. The black conductors supply power to the branch circuits via the circuit breakers and black conductors connected to the breakers.

The white return the power to the Neutral conductor and back to the PoCo equipment. The bare ground conductors are used to keep all metal parts in the residence at the same level.