hope you don't mind me asking, but how do you look at soldier's service records from Georgia?

I have a subscription service to these records.

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I saw in the Atlanta Campaign order of battle, Ferrell's battery is mentioned In Wheeler's Cavalry Corps. The battery commander was Lt. Nathan Davis- do you know where Captain Ferrell was?

I suspect this citation is in error and that Davis was commanding a section of Ferrell's battery. It was quite common for the individual two gun sections of a battery to be temporarily assigned to different organizations. However, Ferrell may have been on sick furlough at the time. Note this citation from the Official Records:

Abstract from return of the Light Artillery in Department of Alabama, Mississippi, and East Louisiana, Lieut. Gen. Richard Taylor commanding, for October 31, 1864; headquarters Selma, Ala

Ferell's Battery, in the field, consisted of: 2 Officers, 80 men & 5 pieces of Artillery

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my grandfather talked about being in Rome, Georgia in mid-may, 1864 during Sherman's March and he said his BATTALION was overrun and as the family story goes, he went some miles back to rescue his brother Francis after the attack. Are you sure Ferrell's battery, or at least a section, was not there?

The only thing sure is that brother Josa was at Rome with one section of the battery as previously noted.