The below logic should be default handled by domo for every no field.
Case
WHEN `Choose Metric` = '$ Sales' and LENGTH(Round(Sum(`sales_12w`)))>=9 THEN Concat (Round(Sum(`sales_12w`)/1000000000,2),'B')
WHEN `Choose Metric` = '$ Sales' and LENGTH(Round(Sum(`sales_12w`)))>=6 THEN Concat (Round(Sum(`sales_12w`)/1000000,2),'M')
WHEN `Choose Metric` = '$ Sales' and LENGTH(Round(Sum(`sales_12w`)))>=3 THEN Concat (Round(Sum(`sales_12w`)/1000,2),'K')
ELSE
Round(Sum(`sales_12w`),2)
END