Use the breaks argument to ggplot2::scale_x_continuous like so:
library(tidyverse)
mtcars %>%
ggplot(aes(x = disp, y = hp)) +
geom_point() +
scale_x_continuous(
breaks = seq(
from = 0, # Adjust the from, to, and by arguments as needed
to = 500,
by = 20
)
)