Create and fill up a blank column with values from a different CSV file

I have a dataframe ABC which contains 2 columns and rows will differ as I update the table in due course.

PORT        COUNTRY
ROTTERDAM   NETHERLANDS
MUMBAI      INDIA
DAKAR       SENEGAL
ROTTERDAM   NETHERLANDS
ZHOUSHAN    CHINA
ZHENJIANG   CHINA
VIZAG       INDIA

and so on. It is an extensive list.

In another dataframe, data I created, the PORT column already exists, but I intend to add the COUNTRY column, so that future analysis becomes easy.

I creted the blanks column by the following code

    data$COUNTRY <- 0

I intend to write a function so as to match the PORT and COUNTRY in the ABC and fill up the COUNTRY column automatically in data.

I have used the merge() function using the following code

data <- merge(data, ABC, by = "PORT", all.x = TRUE)
Error: Error: No common variables. Please specify `by` param.

I have also tried using the inner_join() in the dplyr package. Error : index out of bounds.

Finally, I also tried to write a function so as to load both data frames, compare and fill up data

  fillCountry <- function(x)
{  

countrySize <- length(1 : ABC$PORT)

  for (i in 1:countrySize)


data$country <- if (ABC$PORT[i] == ABC$COUNTRY[i])


return(data)

} 
Error:  Error in Ops.factor(ABC$PORT[i], ABC$COUNTRY[i]) : 
        level sets of factors are different

Please suggest any tool or method and please correct me if I am doing it totally wrong.