To convert a file from iso-8859-1 to UTF-8, just open the terminal, go to the folder where the file is and run the following command:
iconv -f iso-8859-1 -t utf-8 YOUR-ISO-8859-1-FILE.txt > NEW-UTF8-FILE.txt
You can of course use the same command for other encodings, just change the ”-f” (from) encoding and ”-t” (to) encoding.
To find out what encoding a file has, just type:
file -I YOUR-FILE.txt
(it is a capital i)