I think 2 files,header.php and single.php,what theme are you using,look in theme folder do you have single.php?notepade++ have option search in files,so you can easily find word home where and in what files is locate.
If your wordpress theme use gnutext localization you can easaly change that word,but maybe best way is to do is to open some php editor,notepade++ for example,because that word is hardcoded,find it,and then change it.