I am not sure whether you want the date to be formatted as day-month-year or year-month-day. I opted for day-month-year in the following code. This will work if your dates are actually numeric dates and not character strings.
DF <- data.frame(Date = seq.Date(as.Date("2020-01-01"), as.Date("2020-01-10"), by = 1),
Value = 1:10)
library(ggplot2)
ggplot(DF, aes(Date, Value)) + geom_point()

ggplot(DF, aes(Date, Value)) + geom_point() +
scale_x_date(date_labels = "%d-%m-%Y")

Created on 2020-05-25 by the reprex package (v0.3.0)