You appear to be trying to apply an R function to an Excel file.
First you need to read the Excel file into R and then apply the function. It looks like the functionm descr() is in the * summarytools* package which I do not have installed.
In any case try try something like this:
library("readxl")
dat1 <- read_excel("Babies.xlsx")
descr(dat1)
or maybe
summary(dat1)
For general reference you may want to have a look at