You can use geom_col() directly. See the differences between geom_bar() and geom_col() in this link https://ggplot2.tidyverse.org/reference/geom_bar.html
geom_bar() makes the height of the bar proportional to the number of cases in each group If you want the heights of the bars to represent values in the data, use geom_col() instead.
ggplot(data_country)+aes(x=country,y = conversion_rate)+geom_col()