hey im moving into my dorm in a couple days and im thinking of taking my desktop. im just taking my old desktop that i have been using for 4 years

cuz i dont think laptops are woth the money? i dono. anywaysss i want to reformat my computer before i take it so im thinking of buying an external harddrive.
what are the pros and cons?
can ppl hack external hard drives too?
can external harddrive can viruses? can it crash?
IFFF it crashes, is it possible to still get my files back?
does brands matter when buying external hard drives?
lots of questions, i know.
sorry!