Notice that I said semicolon not colon.
Try running the code below. It will make a file called FJCC_data.csv in you working directory. The data frame df that is read back in should be the same as the first three lines of your data. If it loads correctly, inspect FJCC_data.csv with Notepad and see how it looks different than the file that produced the third image in your last Imgur post.
dfOut <- data.frame(ds = c("2018-06-01", "2018-06-02", "2018-06-03"),
y = c(9000, 8881, 8009))
write.csv(dfOut, "FJCC_data.csv", row.names = FALSE, quote = FALSE)
df <- read.csv("FJCC_data.csv", colClasses = c("Date", "numeric"), header = TRUE)
df
#> ds y
#> 1 2018-06-01 9000
#> 2 2018-06-02 8881
#> 3 2018-06-03 8009
Created on 2019-07-27 by the reprex package (v0.2.1)