Question: what does mga pre mean? is it a slang word. Thanks

Let's break up "mga pre.""Pre" is just shortened (casual) version of the word "pare."
"Pare" is a term for "buddy" or "friend," but used for males."Mga" is used to indicate the plural form of the noun, which in this case is "pare."So, "mga pre" means "buddies" or "friends," but used for males.